Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2017	Jan. 01, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax benefit for difference in tax rate	$ 50,000,000	$ 0	$ 0
Unrecognized Tax Benefits	34,000,000	0	0			$ 0
Reduction in net deferred tax liability due to change of corporate income tax rate		495,000,000
Income taxes paid, net	0	18,000,000	2,000,000
Accumulated Other Comprehensive Income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to reclassify certain tax effects from AOCI to retained earnings				$ 0	$ 0
Accumulated Other Comprehensive Income | Accounting Standards Update 2018-02 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adjustment to reclassify certain tax effects from AOCI to retained earnings	$ 0	$ 492,000,000	$ 0