Income taxes - Deferred tax balance sheet presentation (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred taxes presented on the balance sheet
Deferred tax assets, non-current	$ 6,663	$ 5,206	$ 4,368
Deferred tax liabilities, non-current	(11,490)	(10,828)	(11,060)
Net deferred tax liability	$ (4,827)	$ (5,622)	$ (6,692)	$ (8,378)

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
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-Clause i
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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
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-IssueDate 2018-01-01
-Paragraph 81
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-Clause i
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- References

No definition available.

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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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