Financial instruments - Activity in level 3 financial assets (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019
Financial investments measured at FVPL
Changes in fair value measurement, assets [abstract]
Amortization	$ (23)	$ (29)
Level 3 \| Financial investments \| Long-term financial investments measured at FVOCI
Changes in fair value measurement, assets [abstract]
Balance as of January 1	31	19
Additions	0	8
Cash receipts and payments	0	0
(Losses) recognized in consolidated statements of comprehensive (loss)/income	(10)	(7)
Gain/(losses) in consolidated income statements	0	0
Amortization	0	0
Reclassification	0	2
Balance as of June 30	21	22
Level 3 \| Financial investments \| Financial investments measured at FVPL
Changes in fair value measurement, assets [abstract]
Balance as of January 1	61	98
Additions	0	1
Cash receipts and payments	0	0
(Losses) recognized in consolidated statements of comprehensive (loss)/income	0	0
Gain/(losses) in consolidated income statements	3	3
Reclassification	0	0
Balance as of June 30	$ 41	$ 73

Amortisation, Fair Value Measurement, Assets

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Reclassification, Fair Value Measurement, Assets

+ References

No definition available.

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- References

No definition available.

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The amount of assets that are: (a) cash; (b) an equity instrument of another entity; (c) a contractual right: (i) to receive cash or another financial asset from another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially favourable to the entity; or (d) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to receive a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose the entity’s own equity instruments do not include puttable financial instruments classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. [Refer: Financial instruments, class [member]; Financial liabilities]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The gains (losses) including exchange differences recognised in other comprehensive income on the fair value measurement of assets. [Refer: At fair value [member]; Other comprehensive income]

+ References

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The gains (losses) including exchange differences recognised in profit or loss on the fair value measurement of assets. [Refer: At fair value [member]]

+ References

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-Name IFRS
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- Definition

The increase in the fair value measurement of assets resulting from purchases of those assets. [Refer: At fair value [member]]

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-Name IFRS
-Number 13
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- Definition

The decrease in the fair value measurement of assets resulting from sales. [Refer: At fair value [member]]

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