Events after the balance sheet date (Details) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($) $ / shares
Events After Reporting Period [Abstract]
Dividends declared before financial statements authorised for issue, per share(in dollars per share) \| $ / shares	$ 0.21
Dividends declared before financial statements authorized for issue \| $	$ 4,205

The amount of dividends proposed or declared after the reporting period but before financial statements are authorised for issue. Such dividends are not recognised as a liability at the end of the reporting period because no obligation exists at that time.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 137
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_137_a&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 10
-IssueDate 2017-01-01
-Paragraph 13
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=10&date=2017-03-01&anchor=para_13&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_DividendsProposedOrDeclaredBeforeFinancialStatementsAuthorisedForIssueButNotRecognisedAsDistributionToOwners
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration