Past Due Loans, Allowance For Credit Losses, Non-Accrual Loans, and TDRS - Corporate Loans Portfolio Segment By Origination Year (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	$ 7,000
Corporate Loan | Commercial Industrial And Agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
2020	352,025
2019	900,338
2018	1,008,805
2017	569,566
2016	284,532
Prior	533,674
Revolving Loans	1,795,352
Total	5,444,292
Corporate Loan | Commercial Industrial And Agricultural | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	347,347
2019	886,843
2018	969,223
2017	536,226
2016	254,029
Prior	496,992
Revolving Loans	1,684,205
Total	5,174,865
Corporate Loan | Commercial Industrial And Agricultural | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,155
2019	10,109
2018	11,814
2017	4,424
2016	10,296
Prior	14,678
Revolving Loans	65,270
Total	120,746
Corporate Loan | Commercial Industrial And Agricultural | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	523
2019	3,256
2018	25,569
2017	17,947
2016	14,907
Prior	15,875
Revolving Loans	30,769
Total	108,846
Corporate Loan | Commercial Industrial And Agricultural | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	130
2018	2,199
2017	10,969
2016	5,300
Prior	6,129
Revolving Loans	15,108
Total	39,835
Corporate Loan | Commercial Industrial And Agricultural | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1
2018	533
2017	196
2016	398
Prior	1,612
Revolving Loans	3,167
Total	5,907
Corporate Loan | Office, retail, and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	92,076
2019	264,707
2018	271,745
2017	377,611
2016	369,169
Prior	806,158
Revolving Loans	97,602
Total	2,279,068
Corporate Loan | Office, retail, and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	91,286
2019	261,537
2018	269,725
2017	369,944
2016	336,235
Prior	730,037
Revolving Loans	97,171
Total	2,155,935
Corporate Loan | Office, retail, and industrial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	790
2019	3,170
2018	1,888
2017	5,127
2016	20,430
Prior	12,494
Revolving Loans	0
Total	43,899
Corporate Loan | Office, retail, and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	374
2016	626
Prior	33,609
Revolving Loans	0
Total	34,609
Corporate Loan | Office, retail, and industrial | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	132
2017	2,166
2016	11,878
Prior	30,018
Revolving Loans	431
Total	44,625
Corporate Loan | Office, retail, and industrial | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	333
2018	0
2017	0
2016	4
Prior	(8)
Revolving Loans	0
Total	329
Corporate Loan | Multi-family
Financing Receivable, Credit Quality Indicator [Line Items]
2020	64,735
2019	204,728
2018	112,455
2017	105,680
2016	108,810
Prior	276,650
Revolving Loans	33,223
Total	906,281
Corporate Loan | Multi-family | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	64,735
2019	204,728
2018	112,066
2017	103,257
2016	108,573
Prior	263,163
Revolving Loans	33,223
Total	889,745
Corporate Loan | Multi-family | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	7,754
Revolving Loans	0
Total	7,754
Corporate Loan | Multi-family | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	389
2017	84
2016	0
Prior	5,440
Revolving Loans	0
Total	5,913
Corporate Loan | Multi-family | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	2,339
2016	237
Prior	293
Revolving Loans	0
Total	2,869
Corporate Loan | Multi-family | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	4
2018	0
2017	1
2016	0
Prior	0
Revolving Loans	0
Total	5
Corporate Loan | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	6,359
2019	124,887
2018	125,846
2017	93,004
2016	80,257
Prior	99,286
Revolving Loans	33,050
Total	562,689
Corporate Loan | Construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	6,359
2019	124,887
2018	125,846
2017	89,101
2016	66,763
Prior	64,836
Revolving Loans	31,327
Total	509,119
Corporate Loan | Construction | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	2,621
2016	13,494
Prior	1,258
Revolving Loans	0
Total	17,373
Corporate Loan | Construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	7,277
Revolving Loans	0
Total	7,277
Corporate Loan | Construction | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	1,282
2016	0
Prior	25,915
Revolving Loans	1,723
Total	28,920
Corporate Loan | Construction | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	118
2018	0
2017	0
2016	0
Prior	1,690
Revolving Loans	0
Total	1,808
Corporate Loan | Other commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	14,525
2019	168,158
2018	248,142
2017	226,350
2016	116,264
Prior	546,987
Revolving Loans	29,386
Total	1,349,812
Corporate Loan | Other commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	14,525
2019	166,652
2018	241,391
2017	202,227
2016	105,808
Prior	488,295
Revolving Loans	27,508
Total	1,246,406
Corporate Loan | Other commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1,506
2018	6,523
2017	22,233
2016	7,204
Prior	12,288
Revolving Loans	1,300
Total	51,054
Corporate Loan | Other commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	1,409
2016	2,926
Prior	36,166
Revolving Loans	0
Total	40,501
Corporate Loan | Other commercial real estate | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	228
2017	481
2016	326
Prior	10,238
Revolving Loans	578
Total	11,851
Corporate Loan | Other commercial real estate | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	38
2018	1
2017	0
2016	183
Prior	(58)
Revolving Loans	0
Total	164
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total		$ 3,271,117
Consumer loans | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
2020	6,977
2019	12,526
2018	17,614
2017	13,911
2016	12,843
Prior	67,720
Revolving Loans	834,180
Total	965,771	851,454
Consumer loans | Home equity | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	22
2018	110
2017	265
2016	494
Prior	7,159
Revolving Loans	1,453
Total	9,503
Consumer loans | Home equity | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	1
2017	0
2016	1
Prior	51
Revolving Loans	(7)
Total	46
Consumer loans | Home equity | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	6,977
2019	12,504
2018	17,504
2017	13,646
2016	12,349
Prior	60,561
Revolving Loans	832,727
Total	956,268
Consumer loans | 1-4 Family Mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
2020	134,450
2019	798,396
2018	378,819
2017	181,526
2016	196,644
Prior	278,311
Revolving Loans	443
Total	1,968,589
Consumer loans | 1-4 Family Mortgages | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	422
2017	83
2016	63
Prior	8,428
Revolving Loans	0
Total	8,996
Consumer loans | 1-4 Family Mortgages | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	4
2017	0
2016	4
Prior	81
Revolving Loans	0
Total	89
Consumer loans | 1-4 Family Mortgages | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	134,450
2019	798,396
2018	378,397
2017	181,443
2016	196,581
Prior	269,883
Revolving Loans	443
Total	1,959,593
Consumer loans | Installment
Financing Receivable, Credit Quality Indicator [Line Items]
2020	42,072
2019	204,697
2018	120,799
2017	53,601
2016	21,380
Prior	23,003
Revolving Loans	22,963
Total	488,515	$ 492,585
Consumer loans | Installment | Non-accrual
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans	0
Total	0
Consumer loans | Installment | Net Loan Charge Offs
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1,685
2018	1,183
2017	455
2016	52
Prior	391
Revolving Loans	0
Total	3,766
Consumer loans | Installment | Performing Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	42,072
2019	204,697
2018	120,799
2017	53,601
2016	21,380
Prior	23,003
Revolving Loans	22,963
Total	$ 488,515