Statement Of Financial Position [Abstract]

SANTANDER UK PLC - Filing #1998534

Concept	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2023-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2022-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2021-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31	As at 2020-12-31
Statement of financial position [abstract]
Assets [abstract]
Property, plant and equipment	1,494,000,000 GBP	—	—	—	—	—	—	—	—	—	1,513,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Current tax assets	490,000,000 GBP	—	—	—	—	—	—	—	—	—	478,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Cash and cash equivalents	42,502,000,000 GBP	—	—	—	—	—	—	—	—	—	46,484,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	49,254,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	46,697,000,000 GBP	—
Assets	275,448,000,000 GBP	—	—	—	—	—	—	—	—	—	285,213,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Equity and liabilities [abstract]
Equity [abstract]
Issued capital	3,105,000,000 GBP	—	—	—	—	—	—	—	—	—	3,105,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Retained earnings	4,295,000,000 GBP	—	—	—	—	—	—	—	—	—	4,848,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Share premium	5,620,000,000 GBP	—	—	—	—	—	—	—	—	—	5,620,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Other equity interest	1,956,000,000 GBP	—	—	—	—	—	—	—	—	—	1,956,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Other reserves	353,000,000 GBP	—	—	—	—	—	—	—	—	—	1,122,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Equity	14,623,000,000 GBP	4,295,000,000 GBP	— GBP	5,620,000,000 GBP	3,105,000,000 GBP	1,000,000 GBP	14,623,000,000 GBP	348,000,000 GBP	6,000,000 GBP	1,956,000,000 GBP	14,407,000,000 GBP	— GBP	5,620,000,000 GBP	4,848,000,000 GBP	3,105,000,000 GBP	1,000,000 GBP	14,407,000,000 GBP	1,956,000,000 GBP	5,000,000 GBP	1,128,000,000 GBP	5,053,000,000 GBP	2,191,000,000 GBP	16,102,000,000 GBP	107,000,000 GBP	25,000,000 GBP	16,102,000,000 GBP	— GBP	5,620,000,000 GBP	1,000,000 GBP	3,105,000,000 GBP	4,348,000,000 GBP	162,000,000 GBP	481,000,000 GBP	15,774,000,000 GBP	3,105,000,000 GBP	2,191,000,000 GBP	1,000,000 GBP	5,620,000,000 GBP	15,936,000,000 GBP	28,000,000 GBP
Liabilities [abstract]
Provisions [abstract]
Provisions	402,000,000 GBP	—	—	—	—	—	—	—	—	—	378,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Liabilities	260,825,000,000 GBP	—	—	—	—	—	—	—	—	—	270,806,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—
Equity and liabilities	275,448,000,000 GBP	—	—	—	—	—	—	—	—	—	285,213,000,000 GBP	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—	—