Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1,	$ 71	$ 65	$ 74
Additions, based on tax positions related to current year	6	1	2
Additions for tax positions of prior years	6	14	6
Reductions for tax positions of prior years	0	(6)	(6)
Settlements	(2)	0	(7)
Lapses in statutes of limitation	(3)	(3)	(4)
Balance at December 31,	$ 78	$ 71	$ 65