Finance Costs and Unwinding of Obligations (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Disclosure of finance costs and unwinding of obligations [Abstract]
Finance costs	$ 75	$ 69	$ 140
Unwinding of obligations	21	16	38
Finance costs and unwinding of obligations	$ 96	$ 85	$ 178

The amount of expense recognised due to the unwinding of the discount on provisions, resulting from the effect of the passage of time. [Refer: Other provisions]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_ExpenseDueToUnwindingOfDiscountOnProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration