Loans - Residential, Home Equity and Consumer Loans Based on Payment Activity (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 3,978,919		$ 3,977,900
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total	1,061	$ 1,238
Consumer Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	11,092		49,282
Year two	43,922		21,480
Year three	18,492		9,720
Year four	8,005		2,756
Year five	2,400		917
Prior	2,380		1,912
Revolving Loans Amortized Cost Basis	1,717		1,786
Total	88,008		87,853
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	248		1,162
Year two	75		42
Year three	27		23
Year four	15		71
Year five	0		3
Prior	0		1
Revolving Loans Amortized Cost Basis	3		7
Total	368	345	1,309
Consumer Loans | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	11,092		49,208
Year two	43,898		21,459
Year three	18,463		9,708
Year four	7,984		2,756
Year five	2,400		917
Prior	2,377		1,911
Revolving Loans Amortized Cost Basis	1,717		1,783
Total	87,931		87,742
Consumer Loans | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		74
Year two	24		21
Year three	29		12
Year four	21		0
Year five	0		0
Prior	3		1
Revolving Loans Amortized Cost Basis	0		3
Total	77		111
Home Equity Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		0
Year two	238		417
Year three	1,903		488
Year four	303		150
Year five	236		165
Prior	3,536		1,309
Revolving Loans Amortized Cost Basis	306,643		297,156
Total	312,859		299,685
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0		0
Year two	0		0
Year three	35		0
Year four	99		55
Year five	0		0
Prior	0		24
Revolving Loans Amortized Cost Basis	0		15
Total	134	14	94
Home Equity Loans | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		0
Year two	238		170
Year three	1,691		236
Year four	303		90
Year five	236		165
Prior	3,255		1,207
Revolving Loans Amortized Cost Basis	306,632		296,784
Total	312,355		298,652
Home Equity Loans | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		0
Year two	0		247
Year three	212		252
Year four	0		60
Year five	0		0
Prior	281		102
Revolving Loans Amortized Cost Basis	11		372
Total	504		1,033
Residential Mortgage Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	12,231		56,317
Year two	55,043		65,361
Year three	64,121		86,170
Year four	82,977		41,639
Year five	40,223		17,940
Prior	106,641		95,417
Revolving Loans Amortized Cost Basis	0		0
Total	361,236		362,844
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Year one	0		0
Year two	0		0
Year three	0		22
Year four	0		36
Year five	0		0
Prior	0		0
Revolving Loans Amortized Cost Basis	0		0
Total	0	$ 26	58
Residential Mortgage Loans | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	12,231		56,306
Year two	54,893		65,301
Year three	64,121		85,753
Year four	82,933		41,352
Year five	40,025		17,831
Prior	105,460		94,926
Revolving Loans Amortized Cost Basis	0		0
Total	359,663		361,469
Residential Mortgage Loans | Nonperforming
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	0		11
Year two	150		60
Year three	0		417
Year four	44		287
Year five	198		109
Prior	1,181		491
Revolving Loans Amortized Cost Basis	0		0
Total	$ 1,573		$ 1,375