Fair Value (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure	$ 7,092,350,000		$ 7,092,350,000		$ 6,926,294,000
Alternative Investment	46,074,000		46,074,000		44,657,000
Loans Held-for-sale, Fair Value Disclosure	2,866,000		2,866,000		2,149,000
Impaired Financing Receivable, Carrying Value	37,417,000		$ 37,417,000		74,775,000
Discount percentage applied to real estate appraised values			15.00%
Discount percentage applied to lot development appraised values			6.00%
Partial Charge-Offs On Impaired Loans			$ 2,068,000		1,775,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	3,422,000		3,422,000		3,566,000
Impaired Loan Fair Value	2,930,000		2,930,000		5,773,000
Partial Charge-Offs On Impaired Loans carried at Fair Value			1,824,000		1,523,000
Book Value Of Impaired Loans Carried At Fair Value	3,230,000		3,230,000		5,903,000
Impaired Financing Receivable, carried at fair value, related expense	(300,000)	$ 7,000	(900,000)	$ (1,000,000.0)
MSR recorded at lower of cost or fair value	14,960,000	16,191,000	14,960,000	16,191,000	15,792,000	$ 15,237,000	$ 16,470,000	$ 15,264,000
Mortgage Servicing Rights Fair Value	900,000		900,000		1,700,000
Valuation allowance of MSR	85,000	173,000	85,000	173,000	182,000	$ 101,000	$ 232,000	$ 1,568,000
MSRs recorded at cost	14,100,000		14,100,000		14,100,000
Changes due to fair value adjustments	(16,000)	(59,000)	(97,000)	(1,395,000)
Other Real Estate, Foreclosed Assets, and Repossessed Assets	1,354,000		1,354,000		1,354,000
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	19,400,000		19,400,000		20,300,000
Alternative Investment, income recognized	924,000	$ 97,000	683,000	$ 2,600,000
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Alternative Investment	26,700,000		26,700,000		24,400,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure	7,089,454,000		7,089,454,000		6,924,099,000
Impaired Loan Fair Value	2,930,000		2,930,000		5,773,000
Commercial Receivables, excluding Commercial, Financial, and Agricultural [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Financing Receivable, Related Allowance	300,000		300,000		130,000
Financing Receivable, not collateral dependent [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impaired Financing Receivable, Related Allowance	3,122,000		3,122,000		3,436,000
Fair Value, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure	2,930,000		2,930,000		5,773,000
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans Receivable, Fair Value Disclosure	2,930,000		2,930,000		5,773,000
Other Real Estate, Foreclosed Assets, and Repossessed Assets	$ 0		$ 0		$ 0