Loans and Allowance for Credit Losses - Loan Balances by Year of Origination and Internally Assigned Risk Rating (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Total Loan Balance
Current fiscal year	$ 875,940		$ 875,940		$ 1,271,764
Year two	1,301,309		1,301,309		1,214,107
Year three	1,118,263		1,118,263		586,544
Year four	513,435		513,435		725,517
Year five	668,747		668,747		449,759
More than five years	1,712,993		1,712,993		1,528,088
Revolving	1,295,848		1,295,848		1,381,517
Revolving-Term	29,383		29,383		26,673
Total	7,515,918		7,515,918		7,183,969
Current Year-to-date Gross Charge-offs
2023			551
2022			184
2021			191
2020			14
2019			3,529
2018 and Prior			12,874
Revolving			3,143
Revolving-Term			272
Total	4,077	$ 1,239	20,758	$ 9,899
Pass
Total Loan Balance
Current fiscal year	875,940		875,940		1,271,177
Year two	1,300,179		1,300,179		1,177,280
Year three	1,084,087		1,084,087		581,879
Year four	508,448		508,448		677,616
Year five	601,689		601,689		406,053
More than five years	1,493,661		1,493,661		1,313,942
Revolving	1,254,281		1,254,281		1,348,200
Revolving-Term	25,877		25,877		23,596
Total	7,144,162		7,144,162		6,799,743
Special mention
Total Loan Balance
Current fiscal year	0		0		0
Year two	651		651		36,547
Year three	17,961		17,961		146
Year four	3,023		3,023		26,394
Year five	38,236		38,236		24,765
More than five years	118,879		118,879		113,071
Revolving	15,396		15,396		20,073
Revolving-Term	179		179		95
Total	194,325		194,325		221,091
Substandard
Total Loan Balance
Current fiscal year	0		0		587
Year two	479		479		280
Year three	16,215		16,215		4,519
Year four	1,964		1,964		21,507
Year five	28,822		28,822		18,941
More than five years	100,453		100,453		101,043
Revolving	26,171		26,171		13,244
Revolving-Term	3,327		3,327		2,982
Total	177,431		177,431		163,103
Doubtful
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		32
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		32
Commercial Loans | Commercial real estate
Total Loan Balance
Current fiscal year	221,775		221,775		292,732
Year two	268,261		268,261		360,423
Year three	422,345		422,345		269,049
Year four	245,339		245,339		449,493
Year five	426,370		426,370		261,941
More than five years	971,630		971,630		883,535
Revolving	35,469		35,469		21,666
Revolving-Term	0		0		0
Total	2,591,189		2,591,189		2,538,839
Current Year-to-date Gross Charge-offs
2023			0
2022			0
2021			0
2020			0
2019			0
2018 and Prior			0
Revolving			0
Revolving-Term			0
Total	0	628	0	827
Commercial Loans | Commercial and industrial
Total Loan Balance
Current fiscal year	143,170		143,170		253,696
Year two	235,058		235,058		289,448
Year three	224,893		224,893		88,544
Year four	58,238		58,238		73,998
Year five	59,273		59,273		65,911
More than five years	184,340		184,340		147,273
Revolving	519,169		519,169		591,522
Revolving-Term	0		0		0
Total	1,424,141		1,424,141		1,510,392
Current Year-to-date Gross Charge-offs
2023			0
2022			0
2021			0
2020			0
2019			3,412
2018 and Prior			11,808
Revolving			3,033
Revolving-Term			0
Total	3,033	0	18,253	5,797
Commercial Loans | Commercial construction
Total Loan Balance
Current fiscal year	44,519		44,519		120,655
Year two	188,037		188,037		170,691
Year three	97,525		97,525		40,762
Year four	13,266		13,266		14,442
Year five	10,815		10,815		3,953
More than five years	6,202		6,202		4,176
Revolving	12,475		12,475		27,284
Revolving-Term	0		0		0
Total	372,839		372,839		381,963
Current Year-to-date Gross Charge-offs
2023			0
2022			0
2021			0
2020			0
2019			0
2018 and Prior			0
Revolving			0
Revolving-Term			0
Total	0	0	0	0
Commercial Loans | Business banking
Total Loan Balance
Current fiscal year	230,663		230,663		287,679
Year two	270,110		270,110		233,723
Year three	216,729		216,729		91,149
Year four	91,167		91,167		109,731
Year five	102,761		102,761		84,889
More than five years	351,469		351,469		292,211
Revolving	98,585		98,585		105,271
Revolving-Term	1,830		1,830		1,291
Total	1,363,314		1,363,314		1,205,944
Current Year-to-date Gross Charge-offs
2023			0
2022			67
2021			43
2020			1
2019			88
2018 and Prior			1,018
Revolving			35
Revolving-Term			0
Total	590	178	1,252	1,924
Commercial Loans | Pass | Commercial real estate
Total Loan Balance
Current fiscal year	221,775		221,775		292,732
Year two	268,261		268,261		360,423
Year three	416,345		416,345		267,743
Year four	242,965		242,965		422,872
Year five	377,358		377,358		227,006
More than five years	785,748		785,748		704,600
Revolving	35,469		35,469		21,666
Revolving-Term	0		0		0
Total	2,347,921		2,347,921		2,297,042
Commercial Loans | Pass | Commercial and industrial
Total Loan Balance
Current fiscal year	143,170		143,170		253,324
Year two	234,153		234,153		264,012
Year three	199,719		199,719		88,544
Year four	56,549		56,549		63,190
Year five	53,214		53,214		62,874
More than five years	173,188		173,188		138,250
Revolving	478,363		478,363		559,777
Revolving-Term	0		0		0
Total	1,338,356		1,338,356		1,429,971
Commercial Loans | Pass | Commercial construction
Total Loan Balance
Current fiscal year	44,519		44,519		120,655
Year two	188,037		188,037		159,737
Year three	97,525		97,525		40,762
Year four	13,266		13,266		6,338
Year five	2,575		2,575		3,953
More than five years	4,368		4,368		2,297
Revolving	12,475		12,475		27,284
Revolving-Term	0		0		0
Total	362,765		362,765		361,026
Commercial Loans | Pass | Business banking
Total Loan Balance
Current fiscal year	230,663		230,663		287,520
Year two	270,093		270,093		233,499
Year three	213,953		213,953		87,926
Year four	90,386		90,386		107,819
Year five	99,541		99,541		80,549
More than five years	337,456		337,456		276,843
Revolving	98,434		98,434		104,354
Revolving-Term	781		781		645
Total	1,341,307		1,341,307		1,179,155
Commercial Loans | Special mention | Commercial real estate
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	6,000		6,000		0
Year four	1,107		1,107		13,187
Year five	38,236		38,236		20,090
More than five years	106,995		106,995		101,112
Revolving	0		0		0
Revolving-Term	0		0		0
Total	152,338		152,338		134,389
Commercial Loans | Special mention | Commercial and industrial
Total Loan Balance
Current fiscal year	0		0		0
Year two	651		651		25,436
Year three	11,698		11,698		0
Year four	1,689		1,689		5,103
Year five	0		0		1,885
More than five years	8,461		8,461		7,132
Revolving	15,359		15,359		19,280
Revolving-Term	0		0		0
Total	37,858		37,858		58,836
Commercial Loans | Special mention | Commercial construction
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		10,954
Year three	0		0		0
Year four	0		0		8,104
Year five	0		0		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		19,058
Commercial Loans | Special mention | Business banking
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		157
Year three	263		263		146
Year four	227		227		0
Year five	0		0		2,790
More than five years	3,307		3,307		3,945
Revolving	37		37		793
Revolving-Term	179		179		95
Total	4,013		4,013		7,926
Commercial Loans | Substandard | Commercial real estate
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		1,306
Year four	1,267		1,267		13,434
Year five	10,776		10,776		14,845
More than five years	78,887		78,887		77,823
Revolving	0		0		0
Revolving-Term	0		0		0
Total	90,930		90,930		107,408
Commercial Loans | Substandard | Commercial and industrial
Total Loan Balance
Current fiscal year	0		0		372
Year two	254		254		0
Year three	13,476		13,476		0
Year four	0		0		5,705
Year five	6,059		6,059		1,152
More than five years	2,691		2,691		1,891
Revolving	25,447		25,447		12,465
Revolving-Term	0		0		0
Total	47,927		47,927		21,585
Commercial Loans | Substandard | Commercial construction
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	8,240		8,240		0
More than five years	1,834		1,834		1,879
Revolving	0		0		0
Revolving-Term	0		0		0
Total	10,074		10,074		1,879
Commercial Loans | Substandard | Business banking
Total Loan Balance
Current fiscal year	0		0		159
Year two	17		17		67
Year three	2,513		2,513		3,077
Year four	554		554		1,912
Year five	3,220		3,220		1,550
More than five years	10,706		10,706		11,391
Revolving	114		114		124
Revolving-Term	870		870		551
Total	17,994		17,994		18,831
Commercial Loans | Doubtful | Commercial real estate
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		0
Commercial Loans | Doubtful | Commercial and industrial
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		0
Commercial Loans | Doubtful | Commercial construction
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		0
Commercial Loans | Doubtful | Business banking
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		32
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		32
Consumer Loans | Consumer real estate
Total Loan Balance
Current fiscal year	225,529		225,529		296,948
Year two	326,707		326,707		149,003
Year three	149,242		149,242		91,613
Year four	101,938		101,938		74,583
Year five	67,984		67,984		32,031
More than five years	198,475		198,475		200,169
Revolving	554,347		554,347		553,649
Revolving-Term	24,834		24,834		23,957
Total	1,649,056		1,649,056		1,421,953
Current Year-to-date Gross Charge-offs
2023			0
2022			1
2021			0
2020			5
2019			1
2018 and Prior			43
Revolving			75
Revolving-Term			99
Total	107	161	224	299
Consumer Loans | Other consumer
Total Loan Balance
Current fiscal year	10,284		10,284		20,054
Year two	13,136		13,136		10,819
Year three	7,529		7,529		5,427
Year four	3,487		3,487		3,270
Year five	1,544		1,544		1,034
More than five years	877		877		724
Revolving	75,803		75,803		82,125
Revolving-Term	2,719		2,719		1,425
Total	115,379		115,379		124,878
Current Year-to-date Gross Charge-offs
2023			551
2022			116
2021			148
2020			8
2019			28
2018 and Prior			5
Revolving			0
Revolving-Term			173
Total	347	$ 272	1,029	$ 1,052
Consumer Loans | Pass | Consumer real estate
Total Loan Balance
Current fiscal year	225,529		225,529		296,900
Year two	326,499		326,499		148,790
Year three	149,042		149,042		91,477
Year four	101,799		101,799		74,155
Year five	67,478		67,478		30,658
More than five years	192,173		192,173		191,228
Revolving	553,737		553,737		552,994
Revolving-Term	22,393		22,393		21,547
Total	1,638,650		1,638,650		1,407,749
Consumer Loans | Pass | Other consumer
Total Loan Balance
Current fiscal year	10,284		10,284		20,046
Year two	13,136		13,136		10,819
Year three	7,503		7,503		5,427
Year four	3,483		3,483		3,242
Year five	1,523		1,523		1,013
More than five years	728		728		724
Revolving	75,803		75,803		82,125
Revolving-Term	2,703		2,703		1,404
Total	115,163		115,163		124,800
Consumer Loans | Special mention | Consumer real estate
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	116		116		882
Revolving	0		0		0
Revolving-Term	0		0		0
Total	116		116		882
Consumer Loans | Special mention | Other consumer
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		0
Consumer Loans | Substandard | Consumer real estate
Total Loan Balance
Current fiscal year	0		0		48
Year two	208		208		213
Year three	200		200		136
Year four	139		139		428
Year five	506		506		1,373
More than five years	6,186		6,186		8,059
Revolving	610		610		655
Revolving-Term	2,441		2,441		2,410
Total	10,290		10,290		13,322
Consumer Loans | Substandard | Other consumer
Total Loan Balance
Current fiscal year	0		0		8
Year two	0		0		0
Year three	26		26		0
Year four	4		4		28
Year five	21		21		21
More than five years	149		149		0
Revolving	0		0		0
Revolving-Term	16		16		21
Total	216		216		78
Consumer Loans | Doubtful | Consumer real estate
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	0		0		0
Consumer Loans | Doubtful | Other consumer
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		0
Year three	0		0		0
Year four	0		0		0
Year five	0		0		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	$ 0		$ 0		$ 0