Loans Receivable - Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Credit quality indicators
Year one	$ 873,647		$ 873,647		$ 1,684,565
Year two	1,548,796		1,548,796		2,448,570
Year three	2,191,860		2,191,860		1,785,396
Year four	1,629,889		1,629,889		1,190,115
Year five	1,088,571		1,088,571		762,754
Prior	2,839,666		2,839,666		2,364,506
Revolving loans	1,101,343		1,101,343		1,099,359
Revolving loans converted to term loans	80,592		80,592		79,544
Total loans receivable, gross	11,354,364		11,354,364		11,414,809
Total loans receivable, charge-offs	(4,869)	$ (5,244)	(11,528)	$ (9,871)
Revolving loans converted to term loans during the period			10,000		19,000
Special mention and substandard | Minimum
Credit quality indicators
Total loans receivable, gross	1,000		1,000
Personal Banking
Credit quality indicators
Year one	397,207		397,207		947,432
Year two	839,788		839,788		1,463,153
Year three	1,308,781		1,308,781		1,303,418
Year four	1,181,295		1,181,295		788,790
Year five	720,919		720,919		408,938
Prior	1,558,565		1,558,565		1,294,629
Revolving loans	531,194		531,194		530,255
Revolving loans converted to term loans	46,863		46,863		45,455
Total loans receivable, gross	6,584,612		6,584,612		6,782,070
Total loans receivable, charge-offs	(3,050)	(3,552)	(8,197)	(6,657)
Personal Banking | Residential mortgage loans
Credit quality indicators
Year one	16,707		16,707		186,081
Year two	197,517		197,517		666,960
Year three	648,575		648,575		792,488
Year four	771,204		771,204		507,320
Year five	488,847		488,847		244,989
Prior	1,201,218		1,201,218		1,030,347
Revolving loans	0		0		0
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	3,324,068		3,324,068		3,428,185
Year one, charge-offs			0		0
Year two, charge-offs			0		(9)
Year three, charge-offs			(250)		(5)
Year four, charge-offs			0		(130)
Year five, charge-offs			(114)		(23)
Prior, charge-offs			(50)		(1,023)
Revolving loans, charge-offs			0		0
Revolving loans converted to term loans, charge-offs			0		0
Total loans receivable, charge-offs	(252)	(545)	(414)	(752)	(1,189)
Personal Banking | Residential mortgage loans | Pass
Credit quality indicators
Year one	16,707		16,707		186,081
Year two	197,466		197,466		665,379
Year three	646,931		646,931		792,488
Year four	770,828		770,828		506,068
Year five	488,009		488,009		244,678
Prior	1,192,427		1,192,427		1,019,152
Revolving loans	0		0		0
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	3,312,368		3,312,368		3,413,846
Personal Banking | Residential mortgage loans | Substandard
Credit quality indicators
Year one	0		0		0
Year two	51		51		1,581
Year three	1,644		1,644		0
Year four	376		376		1,252
Year five	838		838		311
Prior	8,791		8,791		11,195
Revolving loans	0		0		0
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	11,700		11,700		14,339
Personal Banking | Home equity loans
Credit quality indicators
Year one	12,105		12,105		71,497
Year two	64,074		64,074		100,875
Year three	94,022		94,022		106,097
Year four	97,430		97,430		146,318
Year five	135,479		135,479		94,179
Prior	264,411		264,411		198,992
Revolving loans	466,893		466,893		465,315
Revolving loans converted to term loans	46,072		46,072		44,585
Total loans receivable, gross	1,180,486		1,180,486		1,227,858
Year one, charge-offs			0		0
Year two, charge-offs			0		(53)
Year three, charge-offs			(40)		(46)
Year four, charge-offs			(2)		0
Year five, charge-offs			0		(48)
Prior, charge-offs			(320)		(352)
Revolving loans, charge-offs			(228)		(144)
Revolving loans converted to term loans, charge-offs			(59)		(209)
Total loans receivable, charge-offs	(237)	(235)	(649)	(399)	(852)
Personal Banking | Home equity loans | Pass
Credit quality indicators
Year one	12,105		12,105		71,497
Year two	64,074		64,074		100,639
Year three	93,892		93,892		106,043
Year four	97,376		97,376		146,121
Year five	135,246		135,246		94,144
Prior	263,136		263,136		197,259
Revolving loans	465,532		465,532		463,868
Revolving loans converted to term loans	44,826		44,826		43,526
Total loans receivable, gross	1,176,187		1,176,187		1,223,097
Personal Banking | Home equity loans | Substandard
Credit quality indicators
Year one	0		0		0
Year two	0		0		236
Year three	130		130		54
Year four	54		54		197
Year five	233		233		35
Prior	1,275		1,275		1,733
Revolving loans	1,361		1,361		1,447
Revolving loans converted to term loans	1,246		1,246		1,059
Total loans receivable, gross	4,299		4,299		4,761
Personal Banking | Vehicle loans
Credit quality indicators
Year one	352,673		352,673		665,522
Year two	559,024		559,024		683,693
Year three	557,497		557,497		399,262
Year four	308,674		308,674		133,074
Year five	95,265		95,265		68,409
Prior	87,795		87,795		58,641
Revolving loans	0		0		0
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	1,960,928		1,960,928		2,008,601
Year one, charge-offs			(61)		(678)
Year two, charge-offs			(1,153)		(1,844)
Year three, charge-offs			(1,261)		(1,967)
Year four, charge-offs			(1,207)		(475)
Year five, charge-offs			(213)		(652)
Prior, charge-offs			(619)		(853)
Revolving loans, charge-offs			0		0
Revolving loans converted to term loans, charge-offs			0		0
Total loans receivable, charge-offs	(1,926)	(1,539)	(4,514)	(3,207)	(6,468)
Personal Banking | Vehicle loans | Pass
Credit quality indicators
Year one	352,639		352,639		664,876
Year two	558,240		558,240		682,275
Year three	556,097		556,097		397,809
Year four	307,322		307,322		132,775
Year five	95,012		95,012		67,853
Prior	87,268		87,268		58,153
Revolving loans	0		0		0
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	1,956,578		1,956,578		2,003,741
Personal Banking | Vehicle loans | Substandard
Credit quality indicators
Year one	34		34		646
Year two	784		784		1,418
Year three	1,400		1,400		1,453
Year four	1,352		1,352		299
Year five	253		253		556
Prior	527		527		488
Revolving loans	0		0		0
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	4,350		4,350		4,860
Personal Banking | Consumer loans
Credit quality indicators
Year one	15,722		15,722		24,332
Year two	19,173		19,173		11,625
Year three	8,687		8,687		5,571
Year four	3,987		3,987		2,078
Year five	1,328		1,328		1,361
Prior	5,141		5,141		6,649
Revolving loans	64,301		64,301		64,940
Revolving loans converted to term loans	791		791		870
Total loans receivable, gross	119,130		119,130		117,426
Year one, charge-offs			202
Year one, charge-offs					(3,412)
Year two, charge-offs			(1,444)		(511)
Year three, charge-offs			(325)		(390)
Year four, charge-offs			(162)		(157)
Year five, charge-offs			(27)		(177)
Prior, charge-offs			(508)		(980)
Revolving loans, charge-offs			(333)		(317)
Revolving loans converted to term loans, charge-offs			(23)		(38)
Total loans receivable, charge-offs	(635)	(1,233)	(2,620)	(2,299)	(5,983)
Personal Banking | Consumer loans | Pass
Credit quality indicators
Year one	15,714		15,714		24,277
Year two	19,085		19,085		11,582
Year three	8,647		8,647		5,552
Year four	3,966		3,966		2,072
Year five	1,328		1,328		1,355
Prior	5,123		5,123		6,603
Revolving loans	63,732		63,732		64,214
Revolving loans converted to term loans	696		696		820
Total loans receivable, gross	118,291		118,291		116,475
Personal Banking | Consumer loans | Substandard
Credit quality indicators
Year one	8		8		55
Year two	88		88		43
Year three	40		40		19
Year four	21		21		6
Year five	0		0		6
Prior	18		18		46
Revolving loans	569		569		726
Revolving loans converted to term loans	95		95		50
Total loans receivable, gross	839		839		951
Commercial Banking
Credit quality indicators
Year one	476,440		476,440		737,133
Year two	709,008		709,008		985,417
Year three	883,079		883,079		481,978
Year four	448,594		448,594		401,325
Year five	367,652		367,652		353,816
Prior	1,281,101		1,281,101		1,069,877
Revolving loans	570,149		570,149		569,104
Revolving loans converted to term loans	33,729		33,729		34,089
Total loans receivable, gross	4,769,752		4,769,752		4,632,739
Total loans receivable, charge-offs	(1,819)	(1,692)	(3,331)	(3,214)
Commercial Banking | Commercial real estate loans
Credit quality indicators
Year one	98,605		98,605		228,074
Year two	243,383		243,383		496,247
Year three	537,441		537,441		358,594
Year four	363,696		363,696		356,152
Year five	334,609		334,609		269,479
Prior	1,035,769		1,035,769		866,626
Revolving loans	27,335		27,335		28,373
Revolving loans converted to term loans	24,178		24,178		24,912
Total loans receivable, gross	2,665,016		2,665,016		2,628,457
Year one, charge-offs			0		(14)
Year two, charge-offs			0		0
Year three, charge-offs			(44)		(492)
Year four, charge-offs			(360)		0
Year five, charge-offs			0		(51)
Prior, charge-offs			(445)		(1,741)
Revolving loans, charge-offs			0		0
Revolving loans converted to term loans, charge-offs			0		0
Total loans receivable, charge-offs	(500)	(415)	(849)	(1,072)	(2,298)
Commercial Banking | Commercial real estate loans | Pass
Credit quality indicators
Year one	97,120		97,120		223,335
Year two	236,451		236,451		470,762
Year three	509,501		509,501		303,873
Year four	269,475		269,475		332,620
Year five	300,353		300,353		228,382
Prior	906,187		906,187		745,244
Revolving loans	26,428		26,428		27,583
Revolving loans converted to term loans	24,099		24,099		24,804
Total loans receivable, gross	2,369,614		2,369,614		2,356,603
Commercial Banking | Commercial real estate loans | Special mention
Credit quality indicators
Year one	0		0		2,819
Year two	3,311		3,311		24,735
Year three	25,879		25,879		27,871
Year four	39,250		39,250		5,365
Year five	15,583		15,583		4,053
Prior	17,823		17,823		38,665
Revolving loans	805		805		711
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	102,651		102,651		104,219
Commercial Banking | Commercial real estate loans | Substandard
Credit quality indicators
Year one	1,485		1,485		1,920
Year two	3,621		3,621		750
Year three	2,061		2,061		26,850
Year four	54,971		54,971		18,167
Year five	18,673		18,673		37,044
Prior	111,759		111,759		82,717
Revolving loans	102		102		79
Revolving loans converted to term loans	79		79		108
Total loans receivable, gross	192,751		192,751		167,635
Commercial Banking | Commercial real estate loans - owner occupied
Credit quality indicators
Year one	47,702		47,702		25,946
Year two	27,091		27,091		52,106
Year three	37,878		37,878		48,991
Year four	47,952		47,952		17,650
Year five	16,971		16,971		47,646
Prior	178,679		178,679		147,768
Revolving loans	3,397		3,397		2,378
Revolving loans converted to term loans	2,952		2,952		3,068
Total loans receivable, gross	362,622		362,622		345,553
Year one, charge-offs			0		0
Year two, charge-offs			0		0
Year three, charge-offs			0		0
Year four, charge-offs			0		0
Year five, charge-offs			0		0
Prior, charge-offs			0		(68)
Revolving loans, charge-offs			0		0
Revolving loans converted to term loans, charge-offs			0		0
Total loans receivable, charge-offs	0	(68)	0	(68)	(68)
Commercial Banking | Commercial real estate loans - owner occupied | Pass
Credit quality indicators
Year one	47,702		47,702		24,725
Year two	13,022		13,022		51,986
Year three	34,667		34,667		47,655
Year four	46,645		46,645		15,984
Year five	13,637		13,637		28,614
Prior	152,801		152,801		140,175
Revolving loans	3,397		3,397		2,378
Revolving loans converted to term loans	1,281		1,281		2,390
Total loans receivable, gross	313,152		313,152		313,907
Commercial Banking | Commercial real estate loans - owner occupied | Special mention
Credit quality indicators
Year one	0		0		1,221
Year two	2,200		2,200		120
Year three	3,211		3,211		1,218
Year four	1,307		1,307		0
Year five	0		0		14,386
Prior	21,510		21,510		2,952
Revolving loans	0		0		0
Revolving loans converted to term loans	0		0		0
Total loans receivable, gross	28,228		28,228		19,897
Commercial Banking | Commercial real estate loans - owner occupied | Substandard
Credit quality indicators
Year one	0		0		0
Year two	11,869		11,869		0
Year three	0		0		118
Year four	0		0		1,666
Year five	3,334		3,334		4,646
Prior	4,368		4,368		4,641
Revolving loans	0		0		0
Revolving loans converted to term loans	1,671		1,671		678
Total loans receivable, gross	21,242		21,242		11,749
Commercial Banking | Commercial loans
Credit quality indicators
Year one	330,133		330,133		483,113
Year two	438,534		438,534		437,064
Year three	307,760		307,760		74,393
Year four	36,946		36,946		27,523
Year five	16,072		16,072		36,691
Prior	66,653		66,653		55,483
Revolving loans	539,417		539,417		538,353
Revolving loans converted to term loans	6,599		6,599		6,109
Total loans receivable, gross	1,742,114		1,742,114		1,658,729
Year one, charge-offs			0		(35)
Year two, charge-offs			(47)		(2,072)
Year three, charge-offs			(1,787)		(517)
Year four, charge-offs			(115)		(430)
Year five, charge-offs			(182)		(205)
Prior, charge-offs			(266)		(845)
Revolving loans, charge-offs			(75)		(60)
Revolving loans converted to term loans, charge-offs			(10)		(2)
Total loans receivable, charge-offs	(1,319)	$ (1,209)	(2,482)	$ (2,074)	(4,166)
Commercial Banking | Commercial loans | Pass
Credit quality indicators
Year one	322,393		322,393		482,605
Year two	402,521		402,521		430,378
Year three	298,891		298,891		73,469
Year four	35,474		35,474		26,868
Year five	15,652		15,652		34,090
Prior	64,712		64,712		54,617
Revolving loans	530,098		530,098		531,742
Revolving loans converted to term loans	3,311		3,311		4,110
Total loans receivable, gross	1,673,052		1,673,052		1,637,879
Commercial Banking | Commercial loans | Special mention
Credit quality indicators
Year one	7,740		7,740		508
Year two	27,814		27,814		3,671
Year three	4,871		4,871		52
Year four	583		583		299
Year five	284		284		240
Prior	166		166		26
Revolving loans	4,788		4,788		1,882
Revolving loans converted to term loans	1,154		1,154		0
Total loans receivable, gross	47,400		47,400		6,678
Commercial Banking | Commercial loans | Substandard
Credit quality indicators
Year one	0		0		0
Year two	8,199		8,199		3,015
Year three	3,998		3,998		872
Year four	889		889		356
Year five	136		136		2,361
Prior	1,775		1,775		840
Revolving loans	4,531		4,531		4,729
Revolving loans converted to term loans	2,134		2,134		1,999
Total loans receivable, gross	$ 21,662		$ 21,662		$ 14,172