Financial and capital risk management - Liquidity risk management (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) facility
Liquidity risk
Product price market curves
Credit exposure \| $	$ 5,000
Revolving credit facilities
Product price market curves
Number of Revolving Credit Facilities \| facility	2

The amount of exposure to loss resulting from credit risk. [Refer: Credit risk [member]]

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant