The amount of residual interest in the assets of the entity after deducting all its liabilities.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 1
-IssueDate 2016-01-13
-Paragraph 24
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=1&date=2016-03-30&anchor=para_24_a&doctype=Standard
-URIDate 2016-03-31

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 1
-IssueDate 2016-01-13
-Paragraph 32
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=1&date=2016-03-30&anchor=para_32_a_i&doctype=Standard
-URIDate 2016-03-31

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2016-01-13
-Paragraph 93
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=13&date=2016-03-30&anchor=para_93_a&doctype=Standard
-URIDate 2016-03-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2016-01-13
-Paragraph 93
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=13&date=2016-03-30&anchor=para_93_b&doctype=Standard
-URIDate 2016-03-31

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2016-01-13
-Paragraph 93
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=13&date=2016-03-30&anchor=para_93_e&doctype=Standard
-URIDate 2016-03-31

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_55&doctype=Standard
-URIDate 2016-03-31

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2016-01-13
-Paragraph 78
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2016-03-30&anchor=para_78_e&doctype=Standard
-URIDate 2016-03-31

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

Implementation of IFRS 9 and IFRS 15 - IFRS 15 Revenue from Contracts with Customers (Details) - GBP (£) £ in Millions	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jan. 01, 2017
Disclosure of initial application of standards or interpretations [line items]
Shareholders' equity	£ 48,543	£ 47,952	£ 49,143	£ 47,952
Increase (decrease) due to application of IFRS 15
Disclosure of initial application of standards or interpretations [line items]
Deferred income	14
Shareholders' equity	£ (11)		£ (11)