Past Due Loans, Allowance For Credit Losses, Non-Accrual Loans, and TDRS - Corporate Loans Portfolio Segment By Origination Year (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Total loans
Total	$ 14,788,732		$ 14,788,732		$ 14,751,232
Consumer net loan charge-offs
Revolving loans converted to term loans	12,900	$ 5,200	34,000	$ 29,000
Corporate Loan | Commercial, industrial, agricultural
Total loans
2021	755,086		755,086
2020	645,792		645,792
2019	772,200		772,200
2018	692,598		692,598
2017	353,871		353,871
Prior	495,896		495,896
Revolving Loans	1,339,174		1,339,174
Total	5,054,617		5,054,617
Corporate Loan | Commercial, industrial, agricultural | Pass
Total loans
2021	752,464		752,464
2020	641,813		641,813
2019	723,079		723,079
2018	588,007		588,007
2017	308,785		308,785
Prior	430,650		430,650
Revolving Loans	1,280,272		1,280,272
Total	4,725,070		4,725,070
Corporate Loan | Commercial, industrial, agricultural | Special Mention
Total loans
2021	2,370		2,370
2020	894		894
2019	26,523		26,523
2018	37,174		37,174
2017	20,750		20,750
Prior	32,822		32,822
Revolving Loans	36,094		36,094
Total	156,627		156,627
Corporate Loan | Commercial, industrial, agricultural | Substandard
Total loans
2021	252		252
2020	2,039		2,039
2019	21,011		21,011
2018	64,985		64,985
2017	22,195		22,195
Prior	19,296		19,296
Revolving Loans	21,844		21,844
Total	151,622		151,622
Corporate Loan | Commercial, industrial, agricultural | Non-accrual
Total loans
2021	0		0
2020	1,046		1,046
2019	1,587		1,587
2018	2,432		2,432
2017	2,141		2,141
Prior	13,128		13,128
Revolving Loans	964		964
Total	21,298		21,298
Corporate Loan | Commercial, industrial, agricultural | Net loan charge-offs
Total loans
2021	0		0
2020	835		835
2019	4,738		4,738
2018	4,745		4,745
2017	9,770		9,770
Prior	(873)		(873)
Revolving Loans	2,586		2,586
Total	21,801		21,801
Corporate Loan | Office, retail, and industrial
Total loans
2021	141,901		141,901
2020	139,210		139,210
2019	209,725		209,725
2018	177,117		177,117
2017	261,082		261,082
Prior	822,078		822,078
Revolving Loans	14,479		14,479
Total	1,765,592		1,765,592
Corporate Loan | Office, retail, and industrial | Pass
Total loans
2021	139,452		139,452
2020	138,270		138,270
2019	205,148		205,148
2018	157,894		157,894
2017	238,194		238,194
Prior	727,319		727,319
Revolving Loans	14,479		14,479
Total	1,620,756		1,620,756
Corporate Loan | Office, retail, and industrial | Special Mention
Total loans
2021	1,717		1,717
2020	312		312
2019	4,577		4,577
2018	3,301		3,301
2017	17,234		17,234
Prior	35,009		35,009
Revolving Loans	0		0
Total	62,150		62,150
Corporate Loan | Office, retail, and industrial | Substandard
Total loans
2021	732		732
2020	628		628
2019	0		0
2018	15,922		15,922
2017	5,330		5,330
Prior	39,442		39,442
Revolving Loans	0		0
Total	62,054		62,054
Corporate Loan | Office, retail, and industrial | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	324		324
Prior	20,308		20,308
Revolving Loans	0		0
Total	20,632		20,632
Corporate Loan | Office, retail, and industrial | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	246		246
2018	3,899		3,899
2017	1,023		1,023
Prior	3,643		3,643
Revolving Loans	0		0
Total	8,811		8,811
Corporate Loan | Multi- family
Total loans
2021	220,347		220,347
2020	154,304		154,304
2019	159,113		159,113
2018	84,970		84,970
2017	118,355		118,355
Prior	327,615		327,615
Revolving Loans	18,237		18,237
Total	1,082,941		1,082,941
Corporate Loan | Multi- family | Pass
Total loans
2021	220,347		220,347
2020	154,304		154,304
2019	153,338		153,338
2018	80,207		80,207
2017	117,350		117,350
Prior	277,778		277,778
Revolving Loans	18,237		18,237
Total	1,021,561		1,021,561
Corporate Loan | Multi- family | Special Mention
Total loans
2021	0		0
2020	0		0
2019	5,775		5,775
2018	4,385		4,385
2017	0		0
Prior	31,356		31,356
Revolving Loans	0		0
Total	41,516		41,516
Corporate Loan | Multi- family | Substandard
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	378		378
2017	70		70
Prior	15,966		15,966
Revolving Loans	0		0
Total	16,414		16,414
Corporate Loan | Multi- family | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	935		935
Prior	2,515		2,515
Revolving Loans	0		0
Total	3,450		3,450
Corporate Loan | Multi- family | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	5		5
Prior	(7)		(7)
Revolving Loans	0		0
Total	(2)		(2)
Corporate Loan | Construction
Total loans
2021	62,941		62,941
2020	135,694		135,694
2019	89,579		89,579
2018	133,870		133,870
2017	65,492		65,492
Prior	82,658		82,658
Revolving Loans	24,970		24,970
Total	595,204		595,204
Corporate Loan | Construction | Pass
Total loans
2021	62,941		62,941
2020	135,694		135,694
2019	89,579		89,579
2018	133,832		133,832
2017	62,946		62,946
Prior	73,511		73,511
Revolving Loans	24,970		24,970
Total	583,473		583,473
Corporate Loan | Construction | Special Mention
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	38		38
2017	0		0
Prior	162		162
Revolving Loans	0		0
Total	200		200
Corporate Loan | Construction | Substandard
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	1,392		1,392
Prior	8,288		8,288
Revolving Loans	0		0
Total	9,680		9,680
Corporate Loan | Construction | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	1,154		1,154
Prior	697		697
Revolving Loans	0		0
Total	1,851		1,851
Corporate Loan | Construction | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	1,104		1,104
Prior	49		49
Revolving Loans	41		41
Total	1,194		1,194
Corporate Loan | Other commercial real estate
Total loans
2021	180,456		180,456
2020	167,456		167,456
2019	183,355		183,355
2018	250,009		250,009
2017	170,997		170,997
Prior	433,139		433,139
Revolving Loans	23,543		23,543
Total	1,408,955		1,408,955
Corporate Loan | Other commercial real estate | Pass
Total loans
2021	180,456		180,456
2020	167,456		167,456
2019	157,047		157,047
2018	206,984		206,984
2017	138,750		138,750
Prior	335,895		335,895
Revolving Loans	23,160		23,160
Total	1,209,748		1,209,748
Corporate Loan | Other commercial real estate | Special Mention
Total loans
2021	0		0
2020	0		0
2019	24,396		24,396
2018	12,462		12,462
2017	10,464		10,464
Prior	22,403		22,403
Revolving Loans	0		0
Total	69,725		69,725
Corporate Loan | Other commercial real estate | Substandard
Total loans
2021	0		0
2020	0		0
2019	1,912		1,912
2018	30,358		30,358
2017	20,727		20,727
Prior	58,183		58,183
Revolving Loans	242		242
Total	111,422		111,422
Corporate Loan | Other commercial real estate | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	205		205
2017	1,056		1,056
Prior	16,658		16,658
Revolving Loans	141		141
Total	18,060		18,060
Corporate Loan | Other commercial real estate | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	245		245
2017	11		11
Prior	1,403		1,403
Revolving Loans	0		0
Total	1,659		1,659
Consumer
Total loans
Total	4,497,323		4,497,323		4,194,209
Consumer | Home equity
Total loans
2021	7,471		7,471
2020	10,778		10,778
2019	8,230		8,230
2018	10,103		10,103
2017	8,731		8,731
Prior	55,458		55,458
Revolving Loans	490,355		490,355
Total	591,126		591,126		761,725
Consumer net loan charge-offs
2021	0		0
2020	0		0
2019	0		0
2018	27		27
2017	(42)		(42)
Prior	(347)		(347)
Revolving Loans	(26)		(26)
Total	(388)		(388)
Consumer | Home equity | Performing
Total loans
2021	7,471		7,471
2020	10,778		10,778
2019	8,168		8,168
2018	9,650		9,650
2017	8,508		8,508
Prior	48,409		48,409
Revolving Loans	488,136		488,136
Total	581,120		581,120
Consumer | Home equity | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	62		62
2018	453		453
2017	223		223
Prior	7,049		7,049
Revolving Loans	2,219		2,219
Total	10,006		10,006
Consumer | 1-4 family mortgages
Total loans
2021	908,935		908,935
2020	1,580,084		1,580,084
2019	379,610		379,610
2018	119,463		119,463
2017	74,912		74,912
Prior	269,108		269,108
Revolving Loans	620		620
Total	3,332,732		3,332,732
Consumer net loan charge-offs
2021	0		0
2020	0		0
2019	0		0
2018	2		2
2017	0		0
Prior	247		247
Revolving Loans	0		0
Total	249		249
Consumer | 1-4 family mortgages | Performing
Total loans
2021	908,935		908,935
2020	1,579,102		1,579,102
2019	379,230		379,230
2018	118,836		118,836
2017	74,276		74,276
Prior	258,947		258,947
Revolving Loans	620		620
Total	3,319,946		3,319,946
Consumer | 1-4 family mortgages | Non-accrual
Total loans
2021	0		0
2020	982		982
2019	380		380
2018	627		627
2017	636		636
Prior	10,161		10,161
Revolving Loans	0		0
Total	12,786		12,786
Consumer | Installment
Total loans
2021	165,389		165,389
2020	132,025		132,025
2019	108,820		108,820
2018	74,939		74,939
2017	31,654		31,654
Prior	18,255		18,255
Revolving Loans	42,383		42,383
Total	573,465		573,465		$ 410,071
Consumer net loan charge-offs
2021	247		247
2020	1,323		1,323
2019	2,590		2,590
2018	1,439		1,439
2017	97		97
Prior	(182)		(182)
Revolving Loans	36		36
Total	5,550		5,550
Consumer | Installment | Performing
Total loans
2021	165,389		165,389
2020	132,025		132,025
2019	108,820		108,820
2018	74,939		74,939
2017	31,654		31,654
Prior	18,255		18,255
Revolving Loans	42,383		42,383
Total	573,465		573,465
Consumer | Installment | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	0		0
Prior	0		0
Revolving Loans	0		0
Total	$ 0		$ 0