Loans and advances to customers - Narrative (Details) - GBP (£) £ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule Loans and Advances to Customers [Line Items]
Allowance for expected credit losses	£ 4,084	£ 4,903
Residual value and voluntary terminations
Schedule Loans and Advances to Customers [Line Items]
Allowance for expected credit losses	£ 187	£ 92

The amount of an allowance account used to record impairments to financial assets due to credit losses. [Refer: Financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expired 2023-01-01
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 16
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_16&doctype=Standard&book=b
-URIDate 2023-03-23

Name:	ifrs-full_AllowanceAccountForCreditLossesOfFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant