Income Taxes Income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%	35.00%
Tax Adjustments, Settlements, and Unusual Provisions	$ 45	$ 0	$ 0
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	17
Tax Credit Carryforward, Federal	52
Deferred Tax Assets, Valuation Allowance	0	0
Unrecognized Tax Benefits	$ 0	$ 0