Employees
| Concept | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | As at 2025-03-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Employees | |||||||||||||||||||||||||||||
| Metrics related to human capital diversity | |||||||||||||||||||||||||||||
| Metrics of consolidated subsidiaries | |||||||||||||||||||||||||||||
| Consolidated subsidiaries | 
                                                ㈱博報堂プロダクツ
                                                
                                             | 
                                                ㈱博報堂DYメディアパートナーズ
                                                
                                             | 
                                                ソウルドアウト㈱
                                                
                                             | 
                                                ㈱大広
                                                
                                             | 
                                                ㈱博報堂DYアイ・オー
                                                
                                             | 
                                                ㈱博報堂
                                                
                                             | 
                                                ㈱エッジ・インターナショナル
                                                
                                             | 
                                                ㈱アイヴィジット
                                                
                                             | 
                                                ㈱セレブリックス
                                                
                                             | 
                                                ㈱TBWA\HAKUHODO
                                                
                                             | 
                                                データスタジアム㈱
                                                
                                             | 
                                                ㈱バックスグループ
                                                
                                             | 
                                                ㈱読広クロスコム
                                                
                                             | 
                                                日本トータルテレマーケティング㈱
                                                
                                             | 
                                                ㈱博報堂テクノロジーズ
                                                
                                             | 
                                                ㈱アド・プロ
                                                
                                             | 
                                                ㈱博報堂アイ・スタジオ
                                                
                                             | 
                                                ㈱読売広告社
                                                
                                             | 
                                                ㈱ベストコ
                                                
                                             | 
                                                アイビーシステム㈱
                                                
                                             | 
                                                デジタル・アドバタイジング・コンソーシアム㈱
                                                
                                             | 
                                                ㈱博報堂DYトータルサポート
                                                
                                             | 
                                                ㈱大広WEDO
                                                
                                             | 
                                                ㈱九州博報堂
                                                
                                             | 
                                                ㈱アイレップ
                                                
                                             | 
                                                ㈱オズマピーアール
                                                
                                             | 
                                                ㈱スパイスボックス
                                                
                                             | 
                                                ㈱博報堂Gravity
                                                
                                             | 
                                                ㈱エクスペリエンスD
                                                
                                             | 
| Ratio of female employees in managerial positions | 
                                                0.184
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.063
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.196
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.076
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.708
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.104
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.364
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.316
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.171
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.261
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.067
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.148
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.125
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.336
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.154
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.809
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.159
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.070
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.044
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.250
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.249
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.419
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.191
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.107
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.258
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.286
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.154
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.273
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Ratio of male employees taking childcare leave | |||||||||||||||||||||||||||||
| All employees | 
                                                0.615
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.889
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.900
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.769
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.879
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.647
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.778
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.700
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.600
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.897
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.905
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.333
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Regular employees | 
                                                0.579
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.882
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.900
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.769
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.879
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.647
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.600
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.667
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.600
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.897
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.905
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.333
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.500
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Non-regular employees | 
                                                2.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | — | — | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Differences in wages between male and female employees | |||||||||||||||||||||||||||||
| All employees | 
                                                0.844
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.708
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.714
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.720
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.940
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.727
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.713
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.638
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.879
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.682
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.901
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.672
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.752
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.606
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.776
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.877
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.853
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.712
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.653
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.000
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.797
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.793
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.788
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.639
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.743
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.720
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.574
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.753
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.656
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Regular employees | 
                                                0.835
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.752
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.759
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.712
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.024
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.744
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.705
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.889
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.888
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.681
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.859
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.938
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.755
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.767
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.781
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.843
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.857
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.738
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.769
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.889
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.793
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.781
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.809
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.692
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.737
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.737
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.654
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.750
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.509
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
| Non-regular employees | 
                                                0.939
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.945
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.326
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.954
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.426
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.781
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.745
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.779
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.909
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.103
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.910
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.642
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.874
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.803
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | — | 
                                                0.820
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.521
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.986
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.911
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.901
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.822
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.070
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.554
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.796
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                1.049
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.835
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                3.116
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.927
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             | 
                                                0.713
                                                
                                                    
                                                        xbrli:pure
                                                    
                                                
                                             |