Allowance for Credit Losses (Narrative) (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($) contract	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($) contract	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($) contract	Dec. 31, 2021 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Accrued interest related to financial assets held at amortized cost	$ 158,500,000	$ 119,200,000	$ 158,500,000	$ 119,200,000	$ 158,500,000	$ 119,200,000	$ 117,400,000
Nonaccrual loans with no related allowance for credit losses	32,000,000		32,000,000		$ 32,000,000
Loans reasonably expected to be modified into TDRs			8,400,000
Provision for (reversal of) credit losses	6,193,000	$ (7,909,000)	30,711,000	$ (68,584,000)
Loan net charge-offs	3,200,000		15,200,000
Provision for credit losses	$ 227,000		$ 232,000
TDRs, count | contract	7	9	36	45	56	66
Foreclosed residential real estate properties	$ 1,600,000		$ 1,600,000		$ 1,600,000
TDRs, balance	$ 708,000	$ 559,000	$ 6,226,000	$ 6,884,000	13,212,000	$ 12,345,000
Weighted average extension term	42 months	105 months	64 months	108 months
Weighted average decrease in stated interest rate	1.05%	1.29%	0.88%	1.51%
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	43,200,000		$ 43,200,000		43,200,000
TDRs, count | contract			219
Allowance for loan losses related to impaired loans	2,100,000		$ 2,100,000		2,100,000
Financing Receivable | Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Recorded investment, foreclosure proceedings in process	$ 73,100,000	$ 14,300,000	$ 73,100,000	$ 14,300,000	$ 73,100,000	$ 14,300,000