Income Taxes Income taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%
Tax Credit Carryforward, Federal	$ 77
Deferred Tax Assets, Valuation Allowance	0	$ 0
Unrecognized Tax Benefits	0	0
(Amortization) Deferral of net benefits due to Tax Reform	(23)	$ (23)	$ 45
State and Local Income Tax Expense (Benefit), Continuing Operations	$ 1