Loans (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Accrued interest receivable on loans		$ 21,000			$ 21,000		$ 22,100
Total loans	[1]	5,122,582			5,122,582		5,137,838
Nonaccrual loans included in past due loans		5,900			5,900		6,400
Nonaccrual loans current on payment		8,100			8,100		16,900
Residential properties in process of foreclosure		1,400			1,400		1,000
Individually analyzed loans		14,100			14,100		16,600
Carrying value of loan modified in a troubled loan modification (TLM)		5,675			7,096	$ 881
Proceeds from sale of loan					312,886	296,376
Loans charged off					14,648	182	2,413
Collateral Dependent Individually Analyzed
Total loans		7,693			7,693		11,591
Asset Pledged as Collateral
Total loans		2,800,000			2,800,000		2,800,000
Commercial real estate
Total loans	[2]	2,156,750			2,156,750		2,154,504
Carrying value of loan modified in a troubled loan modification (TLM)		5,412			5,412	0
Loans charged off		2,991	$ 0		5,715	$ 0	1,961
Commercial real estate | Combination
Carrying value of loan modified in a troubled loan modification (TLM)				$ 4,300
Proceeds from sale of loan		1,200
Loans charged off		3,000
Commercial real estate | Collateral Dependent Individually Analyzed
Total loans	[3]	$ 5,412			$ 5,412		$ 10,053

[1] Includes net unamortized loan origination costs of $11.6 million and $10.9 million, respectively, at September 30, 2025 and December 31, 2024 and net unamortized premiums on loans purchased from and serviced by other financial institutions of $211 thousand and $242 thousand, respectively, at September 30, 2025 and December 31, 2024.

[2] CRE consists of commercial mortgages primarily secured by non-owner occupied income-producing property, as well as construction and development loans. Construction and development loans are made to businesses for land development or the on-site construction of industrial, commercial, or residential buildings.

[3] Secured by income-producing property.