Loans And Allowance For Credit Losses (Summary Of Net Financial Impact On Interest Income Due To Interest Rate Modifications Below Market For Accruing TDR Loans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Modifications [Line Items]
Decrease In Interest Income Due to Interest Rate Changes For Accruing Troubled Debt Restructurings Loans	$ 0	$ 1
1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Decrease In Interest Income Due to Interest Rate Changes For Accruing Troubled Debt Restructurings Loans	0	1
Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Decrease In Interest Income Due to Interest Rate Changes For Accruing Troubled Debt Restructurings Loans	$ 0	$ 1