Income Taxes (Current and Deferred Amounts of Provision) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 88	$ (82)	$ (256)
State and municipal	(16)	(12)	(22)
Foreign	(203)	(354)	(196)
Deferred:
Federal	7	64	(34)
State and municipal	3	13	4
Foreign	10	115	67
(Provision) benefit for income taxes	$ (111)	$ (256)	$ (437)