The increase (decrease) in the provision for unearned premiums. [Refer: Unearned premiums]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 85
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_85&doctype=Standard
-URIDate 2016-03-31

Name:	ifrs-full_IncreaseDecreaseInProvisionForUnearnedPremium
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

INSURANCE PREMIUM INCOME (Details) - GBP (£) £ in Millions	12 Months Ended
INSURANCE PREMIUM INCOME (Details) - GBP (£) £ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
INSURANCE PREMIUM INCOME (Details) [Line Items]
Increase (decrease) in provision for unearned premium	£ (46)	£ (57)
Third Party Insurer [Member]
INSURANCE PREMIUM INCOME (Details) [Line Items]
Increase (decrease) in provision for unearned premium			£ 1,959