Loans, Leases, and Allowance for Credit Losses (Collateral-Dependent Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost	$ 37	$ 47
Commercial and industrial | Commercial | Single family residential, Agriculture
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost	$ 13	$ 20
Weighted average LTV	36.00%	55.00%
Owner-occupied | Commercial | Office building
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost	$ 10	$ 10
Weighted average LTV	43.00%	47.00%
Term | Commercial real estate | Multi-family, Hotel/Motel, Retail
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost	$ 7	$ 12
Weighted average LTV	41.00%	58.00%
Home equity credit line | Consumer | Single family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost	$ 5	$ 3
Weighted average LTV	37.00%	34.00%
1-4 family residential | Consumer | Single family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortized cost	$ 2	$ 2
Weighted average LTV	51.00%	60.00%