Investments in Unconsolidated Entities - Schedule of Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity method investments	$ 460		$ 434
Measurement alternative method investments	8		7
Total investments in unconsolidated entities	468		$ 441
Equity method investments, combined income statements
Revenues	1,689	$ 1,657
Operating expenses	1,215	1,208
Operating income	474	449
Other income (expense), net	(5)	(1)
Net income	$ 469	$ 448