Loans and Allowance for Credit Losses (Narrative) (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2022 USD ($) Loan	Mar. 31, 2021 USD ($) Loan	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Accrued interest	$ 69,300,000				$ 67,800,000
Base line economic forecast probability percentage	40.00%
Social and climate package passed by legislature	$ 600,000,000,000
Federal reserve interest rate description	four 25-basis point
Nonaccrual loans	$ 42,439,000				55,523,000
TDRs both accruing and nonaccruing	6,500,000				10,600,000
Unfunded commitment to borrowers related to modified TDR	0				0
Loans held for sale	59,877,000				93,069,000
Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	3,600,000				6,800,000
Reduced interest rate	100,000
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		$ 1,900,000
Troubled Debt Restructurings [Member] | Loans With Other Modifications [Member]
Accounts Notes And Loans Receivable [Line Items]
Other modifications	$ 100,000	$ 5,300,000
Slower Near Term Growth S-2 [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for credit losses probability weighting percentage	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		35.00%
Forecast [Member]
Accounts Notes And Loans Receivable [Line Items]
Gross domestic product grow percentage			3.50%	3.00%
Residential Mortgages [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	$ 22,744,000				25,439,000
Loans carried at fair value option	25,000,000.0				41,000,000.0
Unpaid principal balance	25,100,000				40,100,000
Residential Mortgages [Member] | Troubled Debt Restructurings [Member]
Accounts Notes And Loans Receivable [Line Items]
Number of TDRs subsequently defaulted | Loan		1
Recorded Investment		$ 600,000
Consumer [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	9,094,000				11,887,000
Real estate in process of foreclosure	5,600,000				4,400,000
Real estate acquired through foreclosure	2,400,000				2,400,000
Total Commercial And Industrial [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Nonaccrual loans	8,061,000				11,895,000
Commercial Non-Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Paycheck protection program loans	$ 334,800,000				531,100,000
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	$ 3,100,000
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	$ 5,312,000				$ 6,974,000
Commercial Non-Real Estate [Member] | Total Commercial And Industrial [Member] | Minimum [Member] | Total Commercial [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] | Maximum [Member] | Total Commercial [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans term	5 years
Loans percentage of origination fee	5.00%