Fair Value Measurements - Effect of Interest Rate Swap Contracts (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Total interest expense which reflects the effects of cash flow hedges	$ (124)	$ (147)	$ (248)	$ (301)
Hedged item	(5)	(5)	(10)	(10)
Derivative designated as hedging instrument	1	5	4	10
(Loss) earnings from equity investments	$ (3)	$ 7	$ (5)	$ 13

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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