Financial instruments - additional disclosures - Activity in level 3 financial assets (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Reconciliation of changes in fair value measurement, assets [abstract]
Balance as of January 1	$ 3,071
Balance as of December 31	3,605	$ 3,071
Measured at FVOCI [member]
Reconciliation of changes in fair value measurement, assets [abstract]
Balance as of January 1	31
Balance as of December 31	28	31
Measured at FVPL [member]
Reconciliation of changes in fair value measurement, assets [abstract]
Balance as of January 1	184
Balance as of December 31	164	184
Financial investments [member] \| Measured at FVOCI [member]
Reconciliation of changes in fair value measurement, assets [abstract]
Balance as of January 1	31
Balance as of December 31	28	31
Financial investments [member] \| Measured at FVPL [member]
Reconciliation of changes in fair value measurement, assets [abstract]
Balance as of January 1	28
Balance as of December 31	12	28
Financial investments [member] \| Level 3 [member] \| Measured at FVOCI [member]
Reconciliation of changes in fair value measurement, assets [abstract]
Balance as of January 1	31	19
Additions	7	17
Sales	0	0
(Losses) recognized in consolidated statement of comprehensive loss	(10)	(7)
Unrealized gains/(losses) in consolidated income statement	0	0
Amortization	0	0
Reclassification	0	2
Balance as of December 31	28	31
Financial investments [member] \| Level 3 [member] \| Measured at FVPL [member]
Reconciliation of changes in fair value measurement, assets [abstract]
Balance as of January 1	61	98
Additions	2	34
Sales	0	(7)
(Losses) recognized in consolidated statement of comprehensive loss	0	0
Unrealized gains/(losses) in consolidated income statement	(5)	(3)
Amortization	(34)	(61)
Reclassification	0	0
Balance as of December 31	$ 24	$ 61

Amortisation, Fair Value Measurement, Assets

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- Definition

Reclassification, Fair Value Measurement, Assets

+ References

No definition available.

+ Details

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- Definition

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
-Name IFRS
-Number 7
-IssueDate 2020-01-01
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
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-Name IFRS
-Number 7
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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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2020-01-01
-Paragraph 93
-Subparagraph e
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2020-en-r&anchor=para_93_e_ii&doctype=Standard
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2020-01-01
-Paragraph 93
-Subparagraph e
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2020-en-r&anchor=para_93_e_i&doctype=Standard
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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]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2020-01-01
-Paragraph 93
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-Clause iii
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-URIDate 2020-01-01

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- References

No definition available.

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- Definition

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

+ References

+ Details

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