Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Beginning balance	$ 130	$ 107
Additions related to current years' tax positions	2	8
Additions related to prior years' tax positions	37	0
Unrecognized Tax Benefits, Decrease Resulting from Acquisition	(1)
Unrecognized Tax Benefits, Increase Resulting from Acquisition		32
Reductions related to prior years' tax positions	(3)	(14)
Reductions due to lapse of statue of limitations	(9)	(2)
Settlements with tax authorities	(5)	(1)
Ending balance	$ 151	$ 130