Additional information about derivatives financial instruments - Protection for treasury volatility related to tender offer transaction (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative financial instruments.
Derivatives settlement cash outflow (inflow)	$ (324)	$ (67)	$ (240)
Forwards contract - treasury volatility related to tender offer transaction - Bought
Derivative financial instruments.
Derivatives settlement cash outflow (inflow)	$ 16

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.

No definition available.

Name:	ifrs-full_DisclosureOfFinancialInstrumentsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration