Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	$ 58	$ 149
Allocations for bad debt deductions of former thrift subsidiaries included in retained earnings	$ 100	$ 100
Income tax examination no longer subject to prior date	2013