Contingent liabilities and commitments (Details) - GBP (£) £ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2014
Contingent liabilities and commitments
Payments in respect of settlements, reimbursement rights		£ 217
Increase (Decrease) In Current Tax Liability	£ 650
Increase (decrease) in deferred tax liability (asset)	£ 350

The decrease (increase) in reimbursement rights resulting from payments in respect of settlements. [Refer: Gains (losses) arising from settlements, net defined benefit liability (asset); Defined benefit plans [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2016-01-13
-Paragraph 141
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2016-03-30&anchor=para_141_g&doctype=Standard
-URIDate 2016-03-31

Name:	ifrs-full_PaymentsInRespectOfSettlementsReimbursementRights
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration