Allowance for Credit Losses - Credit risk profile of loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Nonperforming loans past due			90 days
Current year	$ 279,816		$ 279,816		$ 410,976
Prior year	443,248		443,248		277,930
Two years before current year	280,411		280,411		468,277
Three years before current year	435,465		435,465		452,136
Four years before current year	389,774		389,774		208,251
Prior	573,793		573,793		486,299
Revolving Loans	208,307		208,307		211,048
Total loans	2,610,814		2,610,814		2,514,917
Current period gross charge offs, Total	3,226	$ 6,936	9,395	$ 16,219
Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	295,602		295,602		359,398
Prior year	287,298		287,298		268,003
Two years before current year	195,574		195,574		252,293
Three years before current year	187,311		187,311		119,148
Four years before current year	91,783		91,783		64,853
Prior	175,499		175,499		152,608
Revolving Loans	109,995		109,995		94,145
Total loans	1,343,062		1,343,062		1,310,448
Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	215		215		176
Prior year	3,487		3,487		477
Two years before current year	776		776		1,349
Three years before current year	935		935		771
Four years before current year	418		418		526
Prior	2,240		2,240		2,371
Revolving Loans	468		468		760
Total loans	8,539		8,539		6,430
Total other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	295,817		295,817		359,574
Prior year	290,785		290,785		268,480
Two years before current year	196,350		196,350		253,642
Three years before current year	188,246		188,246		119,919
Four years before current year	92,201		92,201		65,379
Prior	177,739		177,739		154,979
Revolving Loans	110,463		110,463		94,905
Total loans	1,351,601		1,351,601		1,316,878
Residential | First Liens
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	50,005		50,005		64,953
Prior year	66,570		66,570		47,930
Two years before current year	43,592		43,592		89,205
Three years before current year	80,422		80,422		69,270
Four years before current year	63,146		63,146		37,771
Prior	153,852		153,852		138,824
Revolving Loans	1,788		1,788		2,279
Total loans	459,375		459,375		450,232
Current period gross charge offs, Prior			11		221
Current period gross charge offs, Total			11		221
Residential | First Liens | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	50,005		50,005		64,953
Prior year	66,465		66,465		47,930
Two years before current year	43,592		43,592		89,205
Three years before current year	80,422		80,422		69,090
Four years before current year	63,100		63,100		37,658
Prior	152,136		152,136		136,805
Revolving Loans	1,788		1,788		2,279
Total loans	457,508		457,508		447,920
Residential | First Liens | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Prior year	105		105
Three years before current year					180
Four years before current year	46		46		113
Prior	1,716		1,716		2,019
Total loans	1,867		1,867		2,312
Residential | Home Equity
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	338		338		966
Prior year	933		933		562
Two years before current year	706		706		1,058
Three years before current year	842		842		31
Four years before current year	302		302		181
Prior	1,470		1,470		1,257
Revolving Loans	95,802		95,802		85,443
Total loans	100,393		100,393		89,498
Current period gross charge offs, 2022					22
Current period gross charge offs, 2021			22
Current period gross charge offs, Prior			19		28
Current period gross charge offs, Revolving Loans					51
Current period gross charge offs, Total			41		101
Residential | Home Equity | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	338		338		966
Prior year	933		933		562
Two years before current year	706		706		1,017
Three years before current year	808		808		31
Four years before current year	260		260		143
Prior	1,288		1,288		1,149
Revolving Loans	95,371		95,371		84,723
Total loans	99,704		99,704		88,591
Residential | Home Equity | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Two years before current year					41
Three years before current year	34		34
Four years before current year	42		42		38
Prior	182		182		108
Revolving Loans	431		431		720
Total loans	689		689		907
Residential | Junior Liens
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	16,119		16,119		16,989
Prior year	15,385		15,385		12,410
Two years before current year	10,309		10,309		12,631
Three years before current year	9,885		9,885		6,469
Four years before current year	5,125		5,125		5,260
Prior	11,105		11,105		9,375
Revolving Loans	2,537		2,537		1,578
Total loans	70,465		70,465		64,712
Current period gross charge offs, 2023					15
Current period gross charge offs, Prior			73
Current period gross charge offs, Total			73		15
Residential | Junior Liens | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	16,119		16,119		16,989
Prior year	15,342		15,342		12,371
Two years before current year	10,230		10,230		12,590
Three years before current year	9,865		9,865		6,431
Four years before current year	5,125		5,125		5,200
Prior	11,017		11,017		9,229
Revolving Loans	2,537		2,537		1,578
Total loans	70,235		70,235		64,388
Residential | Junior Liens | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Prior year	43		43		39
Two years before current year	79		79		41
Three years before current year	20		20		38
Four years before current year					60
Prior	88		88		146
Total loans	230		230		324
Residential | All Other Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	7,378		7,378		17,542
Prior year	13,247		13,247		13,123
Two years before current year	7,759		7,759		6,960
Three years before current year	4,937		4,937		4,472
Four years before current year	3,695		3,695		633
Prior	1,806		1,806		1,595
Revolving Loans	108		108		53
Total loans	38,930		38,930		44,378
Current period gross charge offs, 2021					6
Current period gross charge offs, Total					6
Residential | All Other Residential | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	7,378		7,378		17,542
Prior year	10,403		10,403		13,123
Two years before current year	7,687		7,687		6,960
Three years before current year	4,937		4,937		4,392
Four years before current year	3,646		3,646		628
Prior	1,797		1,797		1,559
Revolving Loans	108		108		53
Total loans	35,956		35,956		44,257
Residential | All Other Residential | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Prior year	2,844		2,844
Two years before current year	72		72
Three years before current year					80
Four years before current year	49		49		5
Prior	9		9		36
Total loans	2,974		2,974		121
Consumer | Motor Vehicle
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	217,580		217,580		247,512
Prior year	187,845		187,845		187,480
Two years before current year	130,514		130,514		140,363
Three years before current year	90,363		90,363		37,441
Four years before current year	18,591		18,591		20,416
Prior	8,405		8,405		3,349
Revolving Loans	10		10		11
Total loans	653,308		653,308		636,572
Current period gross charge offs, 2024			250		478
Current period gross charge offs, 2023			1,543		2,692
Current period gross charge offs, 2022			1,799		4,839
Current period gross charge offs, 2021			3,205		1,751
Current period gross charge offs, 2020			649		587
Current period gross charge offs, Prior			207		97
Current period gross charge offs, Total			7,653		10,444
Consumer | Motor Vehicle | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	217,368		217,368		247,368
Prior year	187,404		187,404		187,134
Two years before current year	129,967		129,967		139,251
Three years before current year	89,487		89,487		37,043
Four years before current year	18,349		18,349		20,130
Prior	8,181		8,181		3,290
Revolving Loans	10		10		11
Total loans	650,766		650,766		634,227
Consumer | Motor Vehicle | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	212		212		144
Prior year	441		441		346
Two years before current year	547		547		1,112
Three years before current year	876		876		398
Four years before current year	242		242		286
Prior	224		224		59
Total loans	2,542		2,542		2,345
Consumer | All Other Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	4,397		4,397		11,612
Prior year	6,805		6,805		6,975
Two years before current year	3,470		3,470		3,425
Three years before current year	1,797		1,797		2,236
Four years before current year	1,342		1,342		1,118
Prior	1,101		1,101		579
Revolving Loans	10,218		10,218		5,541
Total loans	29,130		29,130		31,486
Current period gross charge offs, 2024			10		50
Current period gross charge offs, 2023			177		197
Current period gross charge offs, 2022			145		121
Current period gross charge offs, 2021			53		22
Current period gross charge offs, 2020			38		16
Current period gross charge offs, Prior			4		24
Current period gross charge offs, Revolving Loans			127		182
Current period gross charge offs, Total			554		612
Consumer | All Other Consumer | Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	4,394		4,394		11,580
Prior year	6,751		6,751		6,883
Two years before current year	3,392		3,392		3,270
Three years before current year	1,792		1,792		2,161
Four years before current year	1,303		1,303		1,094
Prior	1,080		1,080		576
Revolving Loans	10,181		10,181		5,501
Total loans	28,893		28,893		31,065
Consumer | All Other Consumer | Nonperforming Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current year	3		3		32
Prior year	54		54		92
Two years before current year	78		78		155
Three years before current year	5		5		75
Four years before current year	39		39		24
Prior	21		21		3
Revolving Loans	37		37		40
Total loans	$ 237		$ 237		$ 421