Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 86	$ 78	$ 71
Additions, based on tax positions related to current year	9	8	6
Additions for tax positions of prior years	25	15	6
Reductions for tax positions of prior years	(9)	(1)	0
Settlements	(4)	(1)	(2)
Lapses in statutes of limitation	(9)	(13)	(3)
Ending balance	$ 98	$ 86	$ 78