Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Cash paid for income taxes, net of refunds	$ 560	$ 176	$ 121
Cash paid for interest	150	145	209
Beginning restricted cash	7	17	3,569
Ending restricted cash	$ 4	$ 7	17
Non-cash purchase price consideration			$ 89