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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Total loans
Total	$ 15,035,219		$ 15,035,219		$ 14,751,232
Consumer net loan charge-offs
Revolving loans converted to term loans	9,700	$ 16,800	21,100	$ 23,800
Corporate Loan | Commercial, industrial, agricultural
Total loans
2021	450,791		450,791
2020	722,658		722,658
2019	793,960		793,960
2018	784,986		784,986
2017	382,504		382,504
Prior	570,669		570,669
Revolving Loans	1,245,414		1,245,414
Total	4,950,982		4,950,982
Corporate Loan | Commercial, industrial, agricultural | Pass
Total loans
2021	447,821		447,821
2020	717,836		717,836
2019	732,743		732,743
2018	654,037		654,037
2017	363,744		363,744
Prior	497,033		497,033
Revolving Loans	1,189,785		1,189,785
Total	4,602,999		4,602,999
Corporate Loan | Commercial, industrial, agricultural | Special Mention
Total loans
2021	1,389		1,389
2020	1,767		1,767
2019	32,583		32,583
2018	50,046		50,046
2017	924		924
Prior	25,009		25,009
Revolving Loans	33,922		33,922
Total	145,640		145,640
Corporate Loan | Commercial, industrial, agricultural | Substandard
Total loans
2021	399		399
2020	625		625
2019	18,209		18,209
2018	61,422		61,422
2017	15,454		15,454
Prior	35,961		35,961
Revolving Loans	17,980		17,980
Total	150,050		150,050
Corporate Loan | Commercial, industrial, agricultural | Non-accrual
Total loans
2021	1,182		1,182
2020	2,430		2,430
2019	10,425		10,425
2018	19,481		19,481
2017	2,382		2,382
Prior	12,666		12,666
Revolving Loans	3,727		3,727
Total	52,293		52,293
Corporate Loan | Commercial, industrial, agricultural | Net loan charge-offs
Total loans
2021	0		0
2020	775		775
2019	752		752
2018	4,317		4,317
2017	9,775		9,775
Prior	172		172
Revolving Loans	1,045		1,045
Total	16,836		16,836
Corporate Loan | Office, retail, and industrial
Total loans
2021	87,564		87,564
2020	140,564		140,564
2019	230,176		230,176
2018	200,790		200,790
2017	255,851		255,851
Prior	881,794		881,794
Revolving Loans	10,689		10,689
Total	1,807,428		1,807,428
Corporate Loan | Office, retail, and industrial | Pass
Total loans
2021	87,564		87,564
2020	139,618		139,618
2019	227,270		227,270
2018	173,567		173,567
2017	244,300		244,300
Prior	789,382		789,382
Revolving Loans	10,689		10,689
Total	1,672,390		1,672,390
Corporate Loan | Office, retail, and industrial | Special Mention
Total loans
2021	0		0
2020	314		314
2019	2,906		2,906
2018	5,767		5,767
2017	8,917		8,917
Prior	33,752		33,752
Revolving Loans	0		0
Total	51,656		51,656
Corporate Loan | Office, retail, and industrial | Substandard
Total loans
2021	0		0
2020	632		632
2019	0		0
2018	21,325		21,325
2017	2,465		2,465
Prior	39,476		39,476
Revolving Loans	0		0
Total	63,898		63,898
Corporate Loan | Office, retail, and industrial | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	131		131
2017	169		169
Prior	19,184		19,184
Revolving Loans	0		0
Total	19,484		19,484
Corporate Loan | Office, retail, and industrial | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	261		261
2018	3,899		3,899
2017	1,023		1,023
Prior	3,072		3,072
Revolving Loans	0		0
Total	8,255		8,255
Corporate Loan | Multi- family
Total loans
2021	131,931		131,931
2020	152,933		152,933
2019	160,428		160,428
2018	88,155		88,155
2017	126,449		126,449
Prior	334,850		334,850
Revolving Loans	17,976		17,976
Total	1,012,722		1,012,722
Corporate Loan | Multi- family | Pass
Total loans
2021	131,931		131,931
2020	152,933		152,933
2019	160,428		160,428
2018	77,857		77,857
2017	125,443		125,443
Prior	286,737		286,737
Revolving Loans	17,976		17,976
Total	953,305		953,305
Corporate Loan | Multi- family | Special Mention
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	9,918		9,918
2017	0		0
Prior	35,754		35,754
Revolving Loans	0		0
Total	45,672		45,672
Corporate Loan | Multi- family | Substandard
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	380		380
2017	71		71
Prior	9,879		9,879
Revolving Loans	0		0
Total	10,330		10,330
Corporate Loan | Multi- family | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	935		935
Prior	2,480		2,480
Revolving Loans	0		0
Total	3,415		3,415
Corporate Loan | Multi- family | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	4		4
Prior	(7)		(7)
Revolving Loans	0		0
Total	(3)		(3)
Corporate Loan | Construction
Total loans
2021	38,449		38,449
2020	113,848		113,848
2019	98,665		98,665
2018	135,106		135,106
2017	77,211		77,211
Prior	88,630		88,630
Revolving Loans	25,429		25,429
Total	577,338		577,338
Corporate Loan | Construction | Pass
Total loans
2021	38,449		38,449
2020	113,848		113,848
2019	98,665		98,665
2018	135,066		135,066
2017	74,662		74,662
Prior	77,655		77,655
Revolving Loans	25,429		25,429
Total	563,774		563,774
Corporate Loan | Construction | Special Mention
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	40		40
2017	0		0
Prior	72		72
Revolving Loans	0		0
Total	112		112
Corporate Loan | Construction | Substandard
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	1,395		1,395
Prior	9,088		9,088
Revolving Loans	0		0
Total	10,483		10,483
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	1,815		1,815
Revolving Loans	0		0
Total	2,969		2,969
Corporate Loan | Construction | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	0		0
2017	(10)		(10)
Prior	177		177
Revolving Loans	41		41
Total	208		208
Corporate Loan | Other commercial real estate
Total loans
2021	154,306		154,306
2020	173,606		173,606
2019	175,569		175,569
2018	247,203		247,203
2017	188,003		188,003
Prior	493,637		493,637
Revolving Loans	29,046		29,046
Total	1,461,370		1,461,370
Corporate Loan | Other commercial real estate | Pass
Total loans
2021	154,306		154,306
2020	173,606		173,606
2019	149,218		149,218
2018	216,066		216,066
2017	143,310		143,310
Prior	380,975		380,975
Revolving Loans	28,641		28,641
Total	1,246,122		1,246,122
Corporate Loan | Other commercial real estate | Special Mention
Total loans
2021	0		0
2020	0		0
2019	24,432		24,432
2018	13,724		13,724
2017	22,808		22,808
Prior	39,503		39,503
Revolving Loans	0		0
Total	100,467		100,467
Corporate Loan | Other commercial real estate | Substandard
Total loans
2021	0		0
2020	0		0
2019	1,919		1,919
2018	17,101		17,101
2017	20,747		20,747
Prior	50,957		50,957
Revolving Loans	242		242
Total	90,966		90,966
Corporate Loan | Other commercial real estate | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	312		312
2017	1,138		1,138
Prior	22,202		22,202
Revolving Loans	163		163
Total	23,815		23,815
Corporate Loan | Other commercial real estate | Net loan charge-offs
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	246		246
2017	(62)		(62)
Prior	646		646
Revolving Loans	0		0
Total	830		830
Consumer
Total loans
Total	4,519,464		4,519,464		4,194,209
Consumer | Home equity
Total loans
2021	5,020		5,020
2020	11,149		11,149
2019	8,859		8,859
2018	11,737		11,737
2017	9,472		9,472
Prior	60,030		60,030
Revolving Loans	523,100		523,100
Total	629,367		629,367		761,725
Consumer net loan charge-offs
2021	0		0
2020	0		0
2019	0		0
2018	26		26
2017	(42)		(42)
Prior	(112)		(112)
Revolving Loans	(14)		(14)
Total	(142)		(142)
Consumer | Home equity | Performing
Total loans
2021	5,020		5,020
2020	11,149		11,149
2019	8,859		8,859
2018	11,199		11,199
2017	9,246		9,246
Prior	53,069		53,069
Revolving Loans	520,877		520,877
Total	619,419		619,419
Consumer | Home equity | Non-accrual
Total loans
2021	0		0
2020	0		0
2019	0		0
2018	538		538
2017	226		226
Prior	6,961		6,961
Revolving Loans	2,223		2,223
Total	9,948		9,948
Consumer | 1-4 family mortgages
Total loans
2021	371,229		371,229
2020	1,696,920		1,696,920
2019	683,838		683,838
2018	142,347		142,347
2017	91,498		91,498
Prior	301,941		301,941
Revolving Loans	0		0
Total	3,287,773		3,287,773
Consumer net loan charge-offs
2021	0		0
2020	0		0
2019	0		0
2018	2		2
2017	0		0
Prior	208		208
Revolving Loans	0		0
Total	210		210
Consumer | 1-4 family mortgages | Performing
Total loans
2021	371,229		371,229
2020	1,696,057		1,696,057
2019	683,454		683,454
2018	141,720		141,720
2017	90,860		90,860
Prior	291,895		291,895
Revolving Loans	0		0
Total	3,275,215		3,275,215
Consumer | 1-4 family mortgages | Non-accrual
Total loans
2021	0		0
2020	863		863
2019	384		384
2018	627		627
2017	638		638
Prior	10,046		10,046
Revolving Loans	0		0
Total	12,558		12,558
Consumer | Installment
Total loans
2021	138,273		138,273
2020	148,363		148,363
2019	126,842		126,842
2018	87,780		87,780
2017	37,576		37,576
Prior	25,380		25,380
Revolving Loans	38,110		38,110
Total	602,324		602,324		$ 410,071
Consumer net loan charge-offs
2021	14		14
2020	959		959
2019	2,072		2,072
2018	1,170		1,170
2017	193		193
Prior	(115)		(115)
Revolving Loans	27		27
Total	4,320		4,320
Consumer | Installment | Performing
Total loans
2021	138,273		138,273
2020	148,363		148,363
2019	126,842		126,842
2018	87,780		87,780
2017	37,576		37,576
Prior	25,380		25,380
Revolving Loans	38,110		38,110
Total	602,324		602,324
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