Deferred Taxation - Deferred tax liabilities and assets, prior to offsetting of balances (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	$ 5,832	$ 5,435
Deferred tax assets	(5,714)	(4,899)
Charged/(credited) to the income statement	(289)	516
Tax losses [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	(1,847)	(1,894)
Charged/(credited) to the income statement	164	(30)
Provisions
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	(1,810)	(1,585)
Charged/(credited) to the income statement	(175)	(19)
Capital allowances
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	4,742	4,408
Deferred tax assets	(604)	(154)
Charged/(credited) to the income statement	(181)	461
Unremitted earnings
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	411	454
Capitalised interest
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	387	259
Unrealised exchange losses
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	3	5
Deferred tax assets	(176)	(187)
Charged/(credited) to the income statement	21	57
Tax on unremitted earnings
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Charged/(credited) to the income statement	5	(33)
Post-retirement benefits
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax assets	(346)	(293)
Charged/(credited) to the income statement	18	30
Other temporary differences
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Deferred tax liabilities	289	309
Deferred tax assets	(931)	(786)
Charged/(credited) to the income statement	$ (141)	$ 50

The amount of tax expense or income relating to changes in deferred tax liabilities and deferred tax assets, recognised in profit or loss. [Refer: Deferred tax assets; Deferred tax expense (income); Deferred tax liabilities]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2019-01-01
-Paragraph 81
-Subparagraph g
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_g_ii&doctype=Standard
-URIDate 2019-03-27

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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

+ References

No definition available.

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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 2019-01-01
-Paragraph 81
-Subparagraph g
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_g_i&doctype=Standard
-URIDate 2019-03-27

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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

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