Income taxes -Assets and liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets and liabilities
Assets	$ 6,908	$ 6,638
Liabilities	(1,532)	(1,719)	$ (1,700)
Net deferred tax asset	$ (5,376)	$ (4,919)	$ (5,643)

The amount of deferred tax liabilities or assets. [Refer: Deferred tax liabilities; Deferred tax assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2018-01-01
-Paragraph 81
-Subparagraph g
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2018-03-01&anchor=para_81_g_i&doctype=Standard
-URIDate 2018-03-16

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- References

No definition available.

+ Details

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- Definition

The amount of deferred tax assets net of deferred tax liabilities, when the absolute amount of deferred tax assets is greater than the absolute amount of deferred tax liabilities. [Refer: Deferred tax assets; Deferred tax liabilities]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 12
-IssueDate 2018-01-01
-Paragraph 81
-Subparagraph g
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2018-03-01&anchor=para_81_g_i&doctype=Standard
-URIDate 2018-03-16

+ Details

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- Definition

The amount of deferred tax liabilities net of deferred tax assets, when the absolute amount of deferred tax liabilities is greater than the absolute amount of deferred tax assets. [Refer: Deferred tax assets; Deferred tax liabilities]

+ References

+ Details

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