Loans and Allowance for Credit Losses - Loan Balances by Year of Origination and Internally Assigned Risk Rating (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Total Loan Balance
Current fiscal year	$ 217,628		$ 1,271,764
Year two	1,274,343		1,214,107
Year three	1,192,510		586,544
Year four	561,326		725,517
Year five	710,480		449,759
More than five years	1,898,077		1,528,088
Revolving	1,370,146		1,381,517
Revolving-Term	26,554		26,673
Total	7,251,064		7,183,969
Current Period Gross Charge-offs
2023	189
2022	76
2021	103
2020	3
2019	3,499
2018 and Prior	475
Revolving	25
Revolving-Term	89
Total	4,459	$ 982
Pass
Total Loan Balance
Current fiscal year	217,628		1,271,177
Year two	1,269,599		1,177,280
Year three	1,160,139		581,879
Year four	553,664		677,616
Year five	650,630		406,053
More than five years	1,637,906		1,313,942
Revolving	1,318,455		1,348,200
Revolving-Term	23,411		23,596
Total	6,831,432		6,799,743
Special mention
Total Loan Balance
Current fiscal year	0		0
Year two	4,325		36,547
Year three	32,145		146
Year four	3,152		26,394
Year five	39,614		24,765
More than five years	150,445		113,071
Revolving	31,969		20,073
Revolving-Term	95		95
Total	261,745		221,091
Substandard
Total Loan Balance
Current fiscal year	0		587
Year two	419		280
Year three	226		4,519
Year four	4,510		21,507
Year five	20,236		18,941
More than five years	107,983		101,043
Revolving	17,263		13,244
Revolving-Term	3,048		2,982
Total	153,685		163,103
Doubtful
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	1,743		32
Revolving	2,459		0
Revolving-Term	0		0
Total	4,202		32
Commercial Loans | Commercial real estate
Total Loan Balance
Current fiscal year	59,710		292,732
Year two	264,611		360,423
Year three	379,447		269,049
Year four	260,669		449,493
Year five	447,544		261,941
More than five years	1,090,170		883,535
Revolving	21,283		21,666
Revolving-Term	0		0
Total	2,523,434		2,538,839
Current Period 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
Commercial Loans | Commercial and industrial
Total Loan Balance
Current fiscal year	27,936		253,696
Year two	254,391		289,448
Year three	266,690		88,544
Year four	84,058		73,998
Year five	68,548		65,911
More than five years	206,540		147,273
Revolving	585,356		591,522
Revolving-Term	0		0
Total	1,493,519		1,510,392
Current Period Gross Charge-offs
2023	0
2022	0
2021	0
2020	0
2019	3,412
2018 and Prior	0
Revolving	0
Revolving-Term	0
Total	3,412	0
Commercial Loans | Commercial construction
Total Loan Balance
Current fiscal year	5,249		120,655
Year two	142,639		170,691
Year three	159,422		40,762
Year four	25,115		14,442
Year five	11,856		3,953
More than five years	6,589		4,176
Revolving	25,985		27,284
Revolving-Term	0		0
Total	376,855		381,963
Current Period 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
Commercial Loans | Business banking
Total Loan Balance
Current fiscal year	68,827		287,679
Year two	282,559		233,723
Year three	230,679		91,149
Year four	95,954		109,731
Year five	107,457		84,889
More than five years	369,624		292,211
Revolving	105,467		105,271
Revolving-Term	1,275		1,291
Total	1,261,842		1,205,944
Current Period Gross Charge-offs
2023	0
2022	67
2021	43
2020	0
2019	70
2018 and Prior	447
Revolving	25
Revolving-Term	0
Total	652	606
Commercial Loans | Pass | Commercial real estate
Total Loan Balance
Current fiscal year	59,710		292,732
Year two	264,611		360,423
Year three	379,447		267,743
Year four	258,879		422,872
Year five	409,858		227,006
More than five years	873,354		704,600
Revolving	21,283		21,666
Revolving-Term	0		0
Total	2,267,142		2,297,042
Commercial Loans | Pass | Commercial and industrial
Total Loan Balance
Current fiscal year	27,936		253,324
Year two	249,713		264,012
Year three	241,929		88,544
Year four	81,722		63,190
Year five	58,291		62,874
More than five years	193,317		138,250
Revolving	535,107		559,777
Revolving-Term	0		0
Total	1,388,015		1,429,971
Commercial Loans | Pass | Commercial construction
Total Loan Balance
Current fiscal year	5,249		120,655
Year two	142,639		159,737
Year three	153,978		40,762
Year four	25,115		6,338
Year five	3,703		3,953
More than five years	4,728		2,297
Revolving	25,985		27,284
Revolving-Term	0		0
Total	361,397		361,026
Commercial Loans | Pass | Business banking
Total Loan Balance
Current fiscal year	68,827		287,520
Year two	282,541		233,499
Year three	228,739		87,926
Year four	92,571		107,819
Year five	104,156		80,549
More than five years	351,271		276,843
Revolving	104,495		104,354
Revolving-Term	631		645
Total	1,233,231		1,179,155
Commercial Loans | Special mention | Commercial real estate
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	497		13,187
Year five	26,721		20,090
More than five years	135,007		101,112
Revolving	0		0
Revolving-Term	0		0
Total	162,225		134,389
Commercial Loans | Special mention | Commercial and industrial
Total Loan Balance
Current fiscal year	0		0
Year two	4,325		25,436
Year three	24,761		0
Year four	2,336		5,103
Year five	4,740		1,885
More than five years	8,156		7,132
Revolving	31,111		19,280
Revolving-Term	0		0
Total	75,429		58,836
Commercial Loans | Special mention | Commercial construction
Total Loan Balance
Current fiscal year	0		0
Year two	0		10,954
Year three	5,444		0
Year four	0		8,104
Year five	8,153		0
More than five years	0		0
Revolving	0		0
Revolving-Term	0		0
Total	13,597		19,058
Commercial Loans | Special mention | Business banking
Total Loan Balance
Current fiscal year	0		0
Year two	0		157
Year three	1,940		146
Year four	319		0
Year five	0		2,790
More than five years	6,415		3,945
Revolving	858		793
Revolving-Term	95		95
Total	9,627		7,926
Commercial Loans | Substandard | Commercial real estate
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		1,306
Year four	1,293		13,434
Year five	10,965		14,845
More than five years	81,391		77,823
Revolving	0		0
Revolving-Term	0		0
Total	93,649		107,408
Commercial Loans | Substandard | Commercial and industrial
Total Loan Balance
Current fiscal year	0		372
Year two	353		0
Year three	0		0
Year four	0		5,705
Year five	5,517		1,152
More than five years	3,742		1,891
Revolving	16,679		12,465
Revolving-Term	0		0
Total	26,291		21,585
Commercial Loans | Substandard | Commercial construction
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	1,861		1,879
Revolving	0		0
Revolving-Term	0		0
Total	1,861		1,879
Commercial Loans | Substandard | Business banking
Total Loan Balance
Current fiscal year	0		159
Year two	18		67
Year three			3,077
Year four	3,064		1,912
Year five	3,301		1,550
More than five years	11,938		11,391
Revolving	114		124
Revolving-Term	549		551
Total	18,984		18,831
Commercial Loans | Doubtful | Commercial real estate
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	418		0
Revolving	0		0
Revolving-Term	0		0
Total	418		0
Commercial Loans | Doubtful | Commercial and industrial
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	1,325		0
Revolving	2,459		0
Revolving-Term	0		0
Total	3,784		0
Commercial Loans | Doubtful | Commercial construction
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	0		0
Revolving	0		0
Revolving-Term	0		0
Total	0		0
Commercial Loans | Doubtful | Business banking
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	0		32
Revolving	0		0
Revolving-Term	0		0
Total	0		32
Consumer Loans | Consumer real estate
Total Loan Balance
Current fiscal year	51,356		296,948
Year two	313,616		149,003
Year three	146,669		91,613
Year four	90,738		74,583
Year five	72,474		32,031
More than five years	223,812		200,169
Revolving	553,379		553,649
Revolving-Term	23,531		23,957
Total	1,475,575		1,421,953
Current Period Gross Charge-offs
2023	0
2022	0
2021	0
2020	3
2019	0
2018 and Prior	25
Revolving	0
Revolving-Term	49
Total	77	78
Consumer Loans | Other consumer
Total Loan Balance
Current fiscal year	4,550		20,054
Year two	16,527		10,819
Year three	9,603		5,427
Year four	4,792		3,270
Year five	2,601		1,034
More than five years	1,342		724
Revolving	78,676		82,125
Revolving-Term	1,748		1,425
Total	119,839		124,878
Current Period Gross Charge-offs
2023	189
2022	9
2021	60
2020	0
2019	17
2018 and Prior	3
Revolving	0
Revolving-Term	40
Total	318	$ 298
Consumer Loans | Pass | Consumer real estate
Total Loan Balance
Current fiscal year	51,356		296,900
Year two	313,568		148,790
Year three	146,465		91,477
Year four	90,586		74,155
Year five	72,047		30,658
More than five years	213,915		191,228
Revolving	552,909		552,994
Revolving-Term	21,043		21,547
Total	1,461,889		1,407,749
Consumer Loans | Pass | Other consumer
Total Loan Balance
Current fiscal year	4,550		20,046
Year two	16,527		10,819
Year three	9,581		5,427
Year four	4,791		3,242
Year five	2,575		1,013
More than five years	1,321		724
Revolving	78,676		82,125
Revolving-Term	1,737		1,404
Total	119,758		124,800
Consumer Loans | Special mention | Consumer real estate
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	867		882
Revolving	0		0
Revolving-Term	0		0
Total	867		882
Consumer Loans | Special mention | Other consumer
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	0		0
Revolving	0		0
Revolving-Term	0		0
Total	0		0
Consumer Loans | Substandard | Consumer real estate
Total Loan Balance
Current fiscal year	0		48
Year two	48		213
Year three	204		136
Year four	152		428
Year five	427		1,373
More than five years	9,030		8,059
Revolving	470		655
Revolving-Term	2,488		2,410
Total	12,819		13,322
Consumer Loans | Substandard | Other consumer
Total Loan Balance
Current fiscal year	0		8
Year two	0		0
Year three	22		0
Year four	1		28
Year five	26		21
More than five years	21		0
Revolving	0		0
Revolving-Term	11		21
Total	81		78
Consumer Loans | Doubtful | Consumer real estate
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	0		0
Revolving	0		0
Revolving-Term	0		0
Total	0		0
Consumer Loans | Doubtful | Other consumer
Total Loan Balance
Current fiscal year	0		0
Year two	0		0
Year three	0		0
Year four	0		0
Year five	0		0
More than five years	0		0
Revolving	0		0
Revolving-Term	0		0
Total	$ 0		$ 0