Loans and Allowance for Credit Losses (Narrative) (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) loan	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Accounts Notes And Loans Receivable [Line Items]
Accrued interest	$ 67,800,000	$ 76,200,000
Related party balances of loans	62,900,000	11,600,000
Related party new loans	3,100,000
Related party repayments	3,000,000.0
Short-term borrowings	$ 1,665,061,000	1,667,513,000
Percentage of baseline economic forecast	40.00%
Loans held for sale (includes $41,022 and $0 measured at fair value)	$ 93,069,000	136,063,000
Provision for credit losses	(77,494,000)	602,904,000	$ 47,708,000
Nonaccrual loans	55,523,000	139,879,000
TDRs both accruing and nonaccruing	10,600,000	25,800,000
Unfunded commitment to borrowers related to modified TDR	0	4,600,000
Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	6,800,000	21,600,000
Reduced interest rate	500,000	1,100,000
Number of TDRs subsequently defaulted | loan			0
Troubled Debt Restructurings [Member] | Loans With Extended Amortization Terms Or Other Payment Concessions [Member]
Accounts Notes And Loans Receivable [Line Items]
Extended terms and other payment concessions	7,100,000	1,000,000.0	$ 18,700,000
Troubled Debt Restructurings [Member] | Loans With Other Modifications [Member]
Accounts Notes And Loans Receivable [Line Items]
Other modifications	$ 1,200,000	2,100,000	8,100,000
Troubled Debt Restructurings [Member] | Loans With Significant Covenant Waivers [Member]
Accounts Notes And Loans Receivable [Line Items]
Covenant waivers		400,000	$ 41,300,000
Cumulative Effect, Period of Adoption, Adjustment [Member]
Accounts Notes And Loans Receivable [Line Items]
Increase in the allowance for credit losses		$ 76,700,000
Slower Near Term Growth S-2 [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage of baseline economic forecast	60.00%
Downside Scenario S-1 [Member]
Accounts Notes And Loans Receivable [Line Items]
Weighted average percentage of forecast		65.00%
Downside Scenario S-2 [Member]
Accounts Notes And Loans Receivable [Line Items]
Weighted average percentage of forecast		25.00%
Downside Scenario S-3 [Member]
Accounts Notes And Loans Receivable [Line Items]
Weighted average percentage of forecast		10.00%
FHLB Borrowings [Member]
Accounts Notes And Loans Receivable [Line Items]
Short-term borrowings	$ 1,100,000,000	$ 1,100,000,000
Director [Member]
Accounts Notes And Loans Receivable [Line Items]
Related party new loans	51,000,000.0
Energy Related Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale (includes $41,022 and $0 measured at fair value)		497,000,000
Charge-off		242,600,000
Release of credit loss reserves		82,500,000
Provision for credit losses		160,100,000
Residential Mortgages [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	25,439,000	$ 40,573,000
Loans carried at fair value option	41,000,000.0
Unpaid principal balance	$ 40,100,000
Residential Mortgages [Member] | Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Number of TDRs subsequently defaulted | loan	1	2
Recorded Investment	$ 600,000	$ 800,000
Commercial Non-Real Estate [Member] | Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Number of TDRs subsequently defaulted | loan		2
Recorded Investment		$ 13,400,000
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	11,887,000	23,385,000
Real estate in process of foreclosure	4,400,000	17,200,000
Real estate acquired through foreclosure	2,400,000	$ 3,400,000
Consumer [Member] | Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Number of TDRs subsequently defaulted | loan		1
Recorded Investment		$ 100,000
Total Commercial And Industrial [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	11,895,000	66,692,000
Commercial Non-Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Paycheck protection program loans	531,100,000	2,000,000,000.0
Commercial Non-Real Estate [Member] | Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Equity securities	$ 6,800,000
Commercial Non-Real Estate [Member] | Total Commercial And Industrial [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans interest bearing rate	1.00%
Loans receivable percentage of origination fee description	These loans also earn an origination fee of 1%, 3%, or 5%, depending on the loan size
Nonaccrual loans	$ 6,974,000	$ 52,836,000
Commercial Non-Real Estate [Member] | Total Commercial And Industrial [Member] | Total Commercial [Member] | Minimum [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans term	2 years
Loans percentage of origination fee	1.00%
Commercial Non-Real Estate [Member] | Total Commercial And Industrial [Member] | Total Commercial [Member] | Maximum [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans term	5 years
Loans percentage of origination fee	5.00%