Related party transactions (Narrative) (Details) - Barclays PLC [member]	6 Months Ended
Jun. 30, 2019
Disclosure of transactions between related parties [line items]
Name of ultimate parent of group	Barclays PLC
Ordinary shares [member]
Disclosure of transactions between related parties [line items]
Percentage of issued share capital	100.00%

The name of the ultimate controlling party of the group.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2018-01-01
-Paragraph 13
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=24&date=2018-03-01&anchor=para_13&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 138
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_138_c&doctype=Standard
-URIDate 2018-03-16

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration