Loans and Allowance for Credit Losses - Loan Balances by Year of Origination and Internally Assigned Risk Rating (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Total Loan Balance
Current fiscal year	$ 582,399		$ 582,399		$ 1,271,764
Year two	1,276,537		1,276,537		1,214,107
Year three	1,137,286		1,137,286		586,544
Year four	536,735		536,735		725,517
Year five	685,239		685,239		449,759
More than five years	1,781,601		1,781,601		1,528,088
Revolving	1,292,288		1,292,288		1,381,517
Revolving-Term	27,526		27,526		26,673
Total	7,319,611		7,319,611		7,183,969
Current Year-to-date Gross Charge-offs
2023			378
2022			106
2021			162
2020			4
2019			3,511
2018 and Prior			12,298
Revolving			52
Revolving-Term			170
Total	12,222	$ 7,678	16,681	$ 8,661
Pass
Total Loan Balance
Current fiscal year	582,399		582,399		1,271,177
Year two	1,275,292		1,275,292		1,177,280
Year three	1,104,016		1,104,016		581,879
Year four	534,124		534,124		677,616
Year five	620,203		620,203		406,053
More than five years	1,557,555		1,557,555		1,313,942
Revolving	1,252,040		1,252,040		1,348,200
Revolving-Term	24,269		24,269		23,596
Total	6,949,898		6,949,898		6,799,743
Special mention
Total Loan Balance
Current fiscal year	0		0		0
Year two	683		683		36,547
Year three	29,741		29,741		146
Year four	719		719		26,394
Year five	37,679		37,679		24,765
More than five years	114,334		114,334		113,071
Revolving	10,421		10,421		20,073
Revolving-Term	186		186		95
Total	193,763		193,763		221,091
Substandard
Total Loan Balance
Current fiscal year	0		0		587
Year two	562		562		280
Year three	3,529		3,529		4,519
Year four	1,892		1,892		21,507
Year five	27,357		27,357		18,941
More than five years	109,712		109,712		101,043
Revolving	29,827		29,827		13,244
Revolving-Term	3,071		3,071		2,982
Total	175,950		175,950		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	165,422		165,422		292,732
Year two	260,914		260,914		360,423
Year three	407,499		407,499		269,049
Year four	256,393		256,393		449,493
Year five	436,109		436,109		261,941
More than five years	1,028,519		1,028,519		883,535
Revolving	27,406		27,406		21,666
Revolving-Term	0		0		0
Total	2,582,262		2,582,262		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	199	0	199
Commercial Loans | Commercial and industrial
Total Loan Balance
Current fiscal year	105,455		105,455		253,696
Year two	244,608		244,608		289,448
Year three	237,604		237,604		88,544
Year four	68,605		68,605		73,998
Year five	63,915		63,915		65,911
More than five years	184,219		184,219		147,273
Revolving	521,077		521,077		591,522
Revolving-Term	0		0		0
Total	1,425,483		1,425,483		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			0
Revolving-Term			0
Total	11,808	5,797	15,220	5,798
Commercial Loans | Commercial construction
Total Loan Balance
Current fiscal year	31,718		31,718		120,655
Year two	161,284		161,284		170,691
Year three	111,178		111,178		40,762
Year four	12,574		12,574		14,442
Year five	11,053		11,053		3,953
More than five years	6,383		6,383		4,176
Revolving	15,653		15,653		27,284
Revolving-Term	0		0		0
Total	349,843		349,843		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	148,334		148,334		287,679
Year two	274,376		274,376		233,723
Year three	222,017		222,017		91,149
Year four	92,425		92,425		109,731
Year five	102,393		102,393		84,889
More than five years	348,461		348,461		292,211
Revolving	101,469		101,469		105,271
Revolving-Term	1,396		1,396		1,291
Total	1,290,871		1,290,871		1,205,944
Current Year-to-date Gross Charge-offs
2023			0
2022			67
2021			43
2020			0
2019			70
2018 and Prior			457
Revolving			25
Revolving-Term			0
Total	10	1,141	662	1,746
Commercial Loans | Pass | Commercial real estate
Total Loan Balance
Current fiscal year	165,422		165,422		292,732
Year two	260,914		260,914		360,423
Year three	401,730		401,730		267,743
Year four	254,623		254,623		422,872
Year five	389,410		389,410		227,006
More than five years	842,076		842,076		704,600
Revolving	27,406		27,406		21,666
Revolving-Term	0		0		0
Total	2,341,581		2,341,581		2,297,042
Commercial Loans | Pass | Commercial and industrial
Total Loan Balance
Current fiscal year	105,455		105,455		253,324
Year two	243,592		243,592		264,012
Year three	213,147		213,147		88,544
Year four	68,605		68,605		63,190
Year five	57,598		57,598		62,874
More than five years	172,237		172,237		138,250
Revolving	481,599		481,599		559,777
Revolving-Term	0		0		0
Total	1,342,233		1,342,233		1,429,971
Commercial Loans | Pass | Commercial construction
Total Loan Balance
Current fiscal year	31,718		31,718		120,655
Year two	161,284		161,284		159,737
Year three	111,178		111,178		40,762
Year four	12,574		12,574		6,338
Year five	2,862		2,862		3,953
More than five years	4,538		4,538		2,297
Revolving	15,653		15,653		27,284
Revolving-Term	0		0		0
Total	339,807		339,807		361,026
Commercial Loans | Pass | Business banking
Total Loan Balance
Current fiscal year	148,334		148,334		287,520
Year two	274,358		274,358		233,499
Year three	219,203		219,203		87,926
Year four	91,734		91,734		107,819
Year five	99,085		99,085		80,549
More than five years	331,891		331,891		276,843
Revolving	101,290		101,290		104,354
Revolving-Term	619		619		645
Total	1,266,514		1,266,514		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	5,769		5,769		0
Year four	490		490		13,187
Year five	32,907		32,907		20,090
More than five years	100,813		100,813		101,112
Revolving	0		0		0
Revolving-Term	0		0		0
Total	139,979		139,979		134,389
Commercial Loans | Special mention | Commercial and industrial
Total Loan Balance
Current fiscal year	0		0		0
Year two	683		683		25,436
Year three	23,698		23,698		0
Year four	0		0		5,103
Year five	0		0		1,885
More than five years	9,640		9,640		7,132
Revolving	10,366		10,366		19,280
Revolving-Term	0		0		0
Total	44,387		44,387		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	4,632		4,632		0
More than five years	0		0		0
Revolving	0		0		0
Revolving-Term	0		0		0
Total	4,632		4,632		19,058
Commercial Loans | Special mention | Business banking
Total Loan Balance
Current fiscal year	0		0		0
Year two	0		0		157
Year three	274		274		146
Year four	229		229		0
Year five	140		140		2,790
More than five years	3,762		3,762		3,945
Revolving	55		55		793
Revolving-Term	186		186		95
Total	4,646		4,646		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	1,280		1,280		13,434
Year five	13,792		13,792		14,845
More than five years	85,630		85,630		77,823
Revolving	0		0		0
Revolving-Term	0		0		0
Total	100,702		100,702		107,408
Commercial Loans | Substandard | Commercial and industrial
Total Loan Balance
Current fiscal year	0		0		372
Year two	333		333		0
Year three	759		759		0
Year four	0		0		5,705
Year five	6,317		6,317		1,152
More than five years	2,342		2,342		1,891
Revolving	29,112		29,112		12,465
Revolving-Term	0		0		0
Total	38,863		38,863		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	3,559		3,559		0
More than five years	1,845		1,845		1,879
Revolving	0		0		0
Revolving-Term	0		0		0
Total	5,404		5,404		1,879
Commercial Loans | Substandard | Business banking
Total Loan Balance
Current fiscal year	0		0		159
Year two	18		18		67
Year three	2,540		2,540		3,077
Year four	462		462		1,912
Year five	3,168		3,168		1,550
More than five years	12,808		12,808		11,391
Revolving	124		124		124
Revolving-Term	591		591		551
Total	19,711		19,711		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	124,142		124,142		296,948
Year two	320,303		320,303		149,003
Year three	150,469		150,469		91,613
Year four	102,621		102,621		74,583
Year five	69,752		69,752		32,031
More than five years	212,967		212,967		200,169
Revolving	551,017		551,017		553,649
Revolving-Term	24,250		24,250		23,957
Total	1,555,521		1,555,521		1,421,953
Current Year-to-date Gross Charge-offs
2023			0
2022			0
2021			0
2020			3
2019			1
2018 and Prior			29
Revolving			27
Revolving-Term			57
Total	40	60	117	138
Consumer Loans | Other consumer
Total Loan Balance
Current fiscal year	7,328		7,328		20,054
Year two	15,052		15,052		10,819
Year three	8,519		8,519		5,427
Year four	4,117		4,117		3,270
Year five	2,017		2,017		1,034
More than five years	1,052		1,052		724
Revolving	75,666		75,666		82,125
Revolving-Term	1,880		1,880		1,425
Total	115,631		115,631		124,878
Current Year-to-date Gross Charge-offs
2023			378
2022			39
2021			119
2020			1
2019			28
2018 and Prior			4
Revolving			0
Revolving-Term			113
Total	364	$ 481	682	$ 780
Consumer Loans | Pass | Consumer real estate
Total Loan Balance
Current fiscal year	124,142		124,142		296,900
Year two	320,092		320,092		148,790
Year three	150,267		150,267		91,477
Year four	102,471		102,471		74,155
Year five	69,254		69,254		30,658
More than five years	205,912		205,912		191,228
Revolving	550,426		550,426		552,994
Revolving-Term	21,795		21,795		21,547
Total	1,544,359		1,544,359		1,407,749
Consumer Loans | Pass | Other consumer
Total Loan Balance
Current fiscal year	7,328		7,328		20,046
Year two	15,052		15,052		10,819
Year three	8,491		8,491		5,427
Year four	4,117		4,117		3,242
Year five	1,994		1,994		1,013
More than five years	901		901		724
Revolving	75,666		75,666		82,125
Revolving-Term	1,855		1,855		1,404
Total	115,404		115,404		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	119		119		882
Revolving	0		0		0
Revolving-Term	0		0		0
Total	119		119		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
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	211		211		213
Year three	202		202		136
Year four	150		150		428
Year five	498		498		1,373
More than five years	6,936		6,936		8,059
Revolving	591		591		655
Revolving-Term	2,455		2,455		2,410
Total	11,043		11,043		13,322
Consumer Loans | Substandard | Other consumer
Total Loan Balance
Current fiscal year	0		0		8
Year two	0		0		0
Year three	28		28		0
Year four	0		0		28
Year five	23		23		21
More than five years	151		151		0
Revolving	0		0		0
Revolving-Term	25		25		21
Total	227		227		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