Income Tax Expense (Unrecognized Tax Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 11
Unrecognized Tax Benefits that would Impact Effective Tax Rate, Net of Federal Benefits	8
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits, beginning balance	0	$ 0	$ 0
Additions attributable to tax positions taken in the current year	0	0	0
Additions attributable to tax positions taken in prior years	11	0	0
Reduction attributable to tax positions taken in prior years	0	0	0
Lapse of statute	0	0	0
Unrecognized Tax Benefits, ending balance	$ 11	$ 0	$ 0