Supplemental Cash Flow Statement Disclosures (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Cash, Cash Equivalents and Restricted Cash
Cash and cash equivalents	$ 643	$ 1,798	$ 764	$ 721
Current restricted cash	$ 10	8	$ 9	7
Location of current restricted cash	us-gaap:OtherAssetsCurrent		us-gaap:OtherAssetsCurrent
Cash in assets held for sale			$ 63
Total cash, cash equivalents and restricted cash	$ 653	1,806	$ 836	$ 728
Other Non-cash items
PP&E acquired but not yet paid	$ 300	$ 224