Loans, Leases, and Allowance for Credit Losses (Schedule of Investment of Accruing and Nonaccruing Loans Modified as Troubled Debt Restructurings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	$ 3	$ 1
Loans modified as troubled debt restructurings loans	228	40
Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	2	1
Consumer
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	1	0
Accruing
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	0
Accruing | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	0
Accruing | Consumer
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	0
Nonaccruing
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	3	1
Nonaccruing | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	2	1
Nonaccruing | Consumer
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	1	0
Commercial and industrial | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	2	0
Commercial and industrial | Accruing | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	0
Commercial and industrial | Nonaccruing | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	2	0
Owner-occupied | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	1
Owner-occupied | Accruing | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	0
Owner-occupied | Nonaccruing | Commercial
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	1
1-4 family residential | Consumer
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	1	0
1-4 family residential | Accruing | Consumer
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	0	0
1-4 family residential | Nonaccruing | Consumer
Financing Receivable, Modifications [Line Items]
Financing receivable, modifications, subsequent default, recorded investment	$ 1	$ 0