Leases - Reconciliation between IFRS 16 Right-of-use Assets and Lease Commitments (Details) - USD ($) $ in Millions	Jan. 01, 2019	Jun. 30, 2019	Dec. 31, 2018
Disclosure of leases [Abstract]
Lease liabilities at 1 January 2019	$ 128	$ 194	$ 0
Discounting of lease liabilities	16
Expenses on leases of low value assets	$ 121
Lease commitments at 31 December 2018			$ 265

The amount of payments over the finance lease term that the lessee is or can be required to make, excluding contingent rent, costs for services and taxes to be paid by, and reimbursed to, the lessor, together with any amounts guaranteed by the lessee or by a party related to the lessee.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2019-01-01
-Name IAS
-Number 17
-IssueDate 2018-01-01
-Paragraph 31
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=17&date=2018-03-02&anchor=para_31_b&doctype=Standard&book=b
-URIDate 2018-03-16

Name:	ifrs-full_MinimumFinanceLeasePaymentsPayable
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant