Allowance for Credit Losses (Narrative) (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022 USD ($) contract	Jun. 30, 2021 USD ($) contract	Jun. 30, 2022 USD ($) contract	Jun. 30, 2021 USD ($) contract	Jun. 30, 2022 USD ($) contract	Jun. 30, 2021 USD ($) contract	Dec. 31, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Accrued interest related to financial assets held at amortized cost	$ 130,900,000	$ 119,100,000	$ 130,900,000	$ 119,100,000	$ 130,900,000	$ 119,100,000	$ 117,400,000
Nonaccrual loans with no related allowance for credit losses	25,700,000		25,700,000		$ 25,700,000
Loans reasonably expected to be modified into TDRs			135,000
Provision for (reversal of) credit losses	20,493,000	$ (15,289,000)	24,518,000	$ (60,675,000)
Loan net charge-offs	9,500,000		12,000,000.0
Provision for credit losses	$ (76,000)		$ 5,000
TDRs, count | contract	16	16	29	36	57	93
Foreclosed residential real estate properties	$ 1,800,000		$ 1,800,000		$ 1,800,000
TDRs, balance	$ 2,421,000	$ 4,199,000	$ 5,518,000	$ 6,325,000	13,061,000	$ 19,383,000
Weighted average extension term	63 months	106 months	67 months	108 months
Weighted average decrease in stated interest rate	0.96%	1.83%	0.87%	1.52%
Loan forgiveness	$ 0	$ 0	$ 0	$ 0
Interest-only payment terms			4 months	6 months
Financing Receivable
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans modified in TDRs	45,400,000		$ 45,400,000		45,400,000
TDRs, count | contract			227
Allowance for loan losses related to impaired loans	2,300,000		$ 2,300,000		2,300,000
Financing Receivable | Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Recorded investment, foreclosure proceedings in process	$ 10,900,000	$ 14,200,000	$ 10,900,000	$ 14,200,000	$ 10,900,000	$ 14,200,000