Income Tax (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits
Balance at January 1,	$ 34	$ 22	$ 38
Additions for tax positions of prior years	0	12	0
Reductions for tax positions of prior years	0	0	(4)
Additions for tax positions of current year	0	0	3
Reductions for tax positions of current year	0	0	(2)
Settlements with tax authorities	0	0	(13)
Balance at December 31,	34	34	22
Unrecognized tax benefits that, if recognized would impact the effective rate	$ 34	$ 34	$ 22