Fair Value Measurements - Effect of Interest Rate Swap Contracts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Total interest expense which reflects the effects of cash flow hedges	$ (119)	$ (124)	$ (240)	$ (248)
Hedged item	(4)	(5)	(9)	(10)
Derivative designated as hedging instrument	0	1	0	4
Earnings (loss) from equity investments	$ 14	$ (3)	$ 23	$ (5)