Allowance for Credit Losses - Amortized Cost Basis by Year of Origination and Credit Quality Indicator (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Residential and consumer
Credit quality
2020	$ 1,829,003
2019	2,268,378
2018	1,874,257
2017	1,450,025
2016	994,336
Prior	2,580,223
Revolving Loans Amortized Cost Basis	2,722,313
Revolving Loans Converted to Term Loans Amortized Cost Basis	45,495
Total	13,764,030
Residential
Credit quality
2020	383,040
2019	540,465
2018	481,337
2017	542,777
2016	448,922
Prior	1,294,327
Revolving Loans Amortized Cost Basis	873,142
Revolving Loans Converted to Term Loans Amortized Cost Basis	4,431
Total	4,568,441
Consumer
Credit quality
2020	148,811
2019	364,552
2018	286,738
2017	185,424
2016	92,919
Prior	44,397
Revolving Loans Amortized Cost Basis	369,319
Total	1,492,160
Consumer | 740 and greater
Credit quality
2020	65,206
2019	141,704
2018	120,178
2017	71,525
2016	35,932
Prior	12,451
Revolving Loans Amortized Cost Basis	109,702
Total	556,698
Consumer | 680 - 739
Credit quality
2020	47,584
2019	109,728
2018	87,056
2017	48,728
2016	24,478
Prior	10,094
Revolving Loans Amortized Cost Basis	83,021
Total	410,689
Consumer | 620 - 679
Credit quality
2020	24,185
2019	65,310
2018	43,282
2017	31,318
2016	16,144
Prior	7,013
Revolving Loans Amortized Cost Basis	42,511
Total	229,763
Consumer | 550 - 619
Credit quality
2020	5,881
2019	26,220
2018	22,891
2017	20,874
2016	10,869
Prior	5,467
Revolving Loans Amortized Cost Basis	18,429
Total	110,631
Consumer | Less than 550
Credit quality
2020	1,562
2019	12,306
2018	13,110
2017	10,628
2016	5,397
Prior	2,567
Revolving Loans Amortized Cost Basis	7,777
Total	53,347
Consumer | No Score
Credit quality
2020	3,799
2019	124
2018	125
2017	126
2016	27
Prior	1
Revolving Loans Amortized Cost Basis	34,281
Total	38,483
Consumer | Other
Credit quality
2020	594
2019	9,160
2018	96
2017	2,225
2016	72
Prior	6,804
Revolving Loans Amortized Cost Basis	73,598
Total	92,549
Home equity line
Credit quality
Revolving Loans Amortized Cost Basis	872,563
Revolving Loans Converted to Term Loans Amortized Cost Basis	3,928
Total	876,491
Home equity line | 740 and greater
Credit quality
Revolving Loans Amortized Cost Basis	626,897
Revolving Loans Converted to Term Loans Amortized Cost Basis	858
Total	627,755
Home equity line | 680 - 739
Credit quality
Revolving Loans Amortized Cost Basis	169,547
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,283
Total	170,830
Home equity line | 620 - 679
Credit quality
Revolving Loans Amortized Cost Basis	48,655
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,013
Total	49,668
Home equity line | 550 - 619
Credit quality
Revolving Loans Amortized Cost Basis	14,276
Revolving Loans Converted to Term Loans Amortized Cost Basis	562
Total	14,838
Home equity line | Less than 550
Credit quality
Revolving Loans Amortized Cost Basis	6,661
Revolving Loans Converted to Term Loans Amortized Cost Basis	212
Total	6,873
Home equity line | No Score
Credit quality
Revolving Loans Amortized Cost Basis	6,527
Total	6,527
Commercial and Industrial
Credit quality
2020	1,043,349
2019	376,881
2018	294,811
2017	87,467
2016	69,968
Prior	106,241
Revolving Loans Amortized Cost Basis	1,403,927
Revolving Loans Converted to Term Loans Amortized Cost Basis	41,064
Total	3,423,708
Commercial and Industrial | Pass
Credit quality
2020	989,501
2019	349,261
2018	271,941
2017	76,742
2016	62,113
Prior	68,468
Revolving Loans Amortized Cost Basis	1,182,299
Revolving Loans Converted to Term Loans Amortized Cost Basis	39,617
Total	3,039,942
Commercial and Industrial | Special mention
Credit quality
2020	28,136
2019	9,235
2018	8,460
2017	841
2016	335
Prior	27,174
Revolving Loans Amortized Cost Basis	113,642
Revolving Loans Converted to Term Loans Amortized Cost Basis	509
Total	188,332
Commercial and Industrial | Substandard
Credit quality
2020	16,621
2019	1,724
2018	1,836
2017	2,000
2016	4,321
Prior	9,788
Revolving Loans Amortized Cost Basis	52,225
Revolving Loans Converted to Term Loans Amortized Cost Basis	938
Total	89,453
Commercial and Industrial | Other
Credit quality
2020	9,091
2019	16,661
2018	12,574
2017	7,884
2016	3,199
Prior	811
Revolving Loans Amortized Cost Basis	55,761
Total	105,981
Commercial real estate
Credit quality
2020	171,445
2019	748,091
2018	591,157
2017	504,369
2016	350,894
Prior	1,011,696
Revolving Loans Amortized Cost Basis	45,847
Total	3,423,499
Commercial real estate | Pass
Credit quality
2020	171,445
2019	618,501
2018	523,149
2017	440,549
2016	296,474
Prior	927,232
Revolving Loans Amortized Cost Basis	33,878
Total	3,011,228
Commercial real estate | Special mention
Credit quality
2019	113,286
2018	53,391
2017	62,165
2016	47,790
Prior	66,008
Revolving Loans Amortized Cost Basis	2,999
Total	345,639
Commercial real estate | Substandard
Credit quality
2019	16,304
2018	14,617
2017	1,655
2016	6,630
Prior	17,947
Revolving Loans Amortized Cost Basis	8,970
Total	66,123
Commercial real estate | Other
Credit quality
Prior	509
Total	509
Construction
Credit quality
2020	25,030
2019	167,001
2018	203,255
2017	108,321
2016	26,429
Prior	57,821
Revolving Loans Amortized Cost Basis	30,078
Total	617,935
Construction | Pass
Credit quality
2020	16,615
2019	135,963
2018	192,016
2017	96,137
2016	24,106
Prior	41,457
Revolving Loans Amortized Cost Basis	29,297
Total	535,591
Construction | Special mention
Credit quality
2018	2,152
2017	4,782
Prior	10,850
Revolving Loans Amortized Cost Basis	196
Total	17,980
Construction | Substandard
Credit quality
2018	541
2017	1,840
2016	528
Prior	1,000
Total	3,909
Construction | Other
Credit quality
2020	8,415
2019	31,038
2018	8,546
2017	5,562
2016	1,795
Prior	4,514
Revolving Loans Amortized Cost Basis	585
Total	60,455
Lease financing
Credit quality
2020	57,328
2019	71,388
2018	16,959
2017	21,667
2016	5,204
Prior	65,741
Total	238,287
Lease financing | Pass
Credit quality
2020	45,489
2019	67,806
2018	11,965
2017	18,915
2016	3,764
Prior	59,364
Total	207,303
Lease financing | Special mention
Credit quality
2020	9,142
2019	1,931
2018	4,626
2017	1,545
2016	1,440
Prior	5,854
Total	24,538
Lease financing | Substandard
Credit quality
2020	2,697
2019	1,651
2018	368
2017	1,207
Prior	523
Total	6,446
Commercial Lending
Credit quality
2020	1,297,152
2019	1,363,361
2018	1,106,182
2017	721,824
2016	452,495
Prior	1,241,499
Revolving Loans Amortized Cost Basis	1,479,852
Revolving Loans Converted to Term Loans Amortized Cost Basis	41,064
Total	7,703,429
Residential mortgage
Credit quality
2020	383,040
2019	540,465
2018	481,337
2017	542,777
2016	448,922
Prior	1,294,327
Revolving Loans Amortized Cost Basis	579
Revolving Loans Converted to Term Loans Amortized Cost Basis	503
Total	3,691,950
Residential mortgage | 740 and greater
Credit quality
2020	300,079
2019	411,883
2018	353,197
2017	411,670
2016	362,197
Prior	988,771
Total	2,827,797
Residential mortgage | 680 - 739
Credit quality
2020	50,937
2019	72,139
2018	64,920
2017	65,992
2016	43,666
Prior	161,897
Total	459,551
Residential mortgage | 620 - 679
Credit quality
2020	6,098
2019	12,708
2018	12,060
2017	12,648
2016	10,789
Prior	55,000
Total	109,303
Residential mortgage | 550 - 619
Credit quality
2020	2,006
2019	1,824
2018	3,533
2017	3,389
2016	3,032
Prior	13,329
Total	27,113
Residential mortgage | Less than 550
Credit quality
2018	1,204
2017	1,907
2016	528
Prior	6,324
Total	9,963
Residential mortgage | No Score
Credit quality
2020	15,676
2019	21,603
2018	24,182
2017	23,736
2016	16,298
Prior	51,943
Total	153,438
Residential mortgage | Other
Credit quality
2020	8,244
2019	20,308
2018	22,241
2017	23,435
2016	12,412
Prior	17,063
Revolving Loans Amortized Cost Basis	579
Revolving Loans Converted to Term Loans Amortized Cost Basis	503
Total	$ 104,785