Investments in Unconsolidated Entities - Schedule of Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity method investments	$ 464		$ 464		$ 434
Measurement alternative method investments	7		7		7
Total investments in unconsolidated entities	471		471		$ 441
Equity method investments, combined income statements
Revenues	1,714	$ 1,693	5,058	$ 5,005
Operating expenses	1,241	1,229	3,644	3,635
Operating income	473	464	1,414	1,370
Other income (expense), net	(1)	(2)	(3)	(2)
Net income	$ 472	$ 462	$ 1,411	$ 1,368