Allowance for Credit Losses - Amortized Cost Basis by Year of Origination and Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Credit quality
Total loans and leases	$ 13,279,097	$ 13,211,650	$ 13,076,191
Loans graded
Credit quality
Total loans and leases		6,928,919
Pass
Credit quality
Total loans and leases		6,631,021
Special mention
Credit quality
Total loans and leases		198,845
Substandard
Credit quality
Total loans and leases		99,053
Loss
Credit quality
Total loans and leases	0	0
Residential mortgage
Credit quality
2020	864,559
2019	482,495
2018	389,725
2017	471,962
2016	391,156
Prior	1,089,580
Revolving Loans Amortized Cost Basis	578
Revolving Loans Converted to Term Loans Amortized Cost Basis	163
Total amortized cost basis	3,690,218
Residential mortgage | 740 and greater
Credit quality
2020	728,807
2019	384,248
2018	290,484
2017	361,297
2016	314,971
Prior	830,795
Total amortized cost basis	2,910,602
Residential mortgage | 680 - 739
Credit quality
2020	85,151
2019	53,090
2018	44,616
2017	50,703
2016	39,230
Prior	144,537
Total amortized cost basis	417,327
Residential mortgage | 620 - 679
Credit quality
2020	15,767
2019	7,604
2018	11,460
2017	9,628
2016	7,982
Prior	43,393
Total amortized cost basis	95,834
Residential mortgage | 550 - 619
Credit quality
2019	1,971
2018	2,818
2017	2,920
2016	4,474
Prior	10,144
Total amortized cost basis	22,327
Residential mortgage | Less than 550
Credit quality
2019	861
2018	593
2017	2,916
2016	594
Prior	2,138
Total amortized cost basis	7,102
Residential mortgage | No Score
Credit quality
2020	13,823
2019	18,861
2018	21,214
2017	21,821
2016	14,355
Prior	45,147
Total amortized cost basis	135,221
Residential mortgage | Other
Credit quality
2020	21,011
2019	15,860
2018	18,540
2017	22,677
2016	9,550
Prior	13,426
Revolving Loans Amortized Cost Basis	578
Revolving Loans Converted to Term Loans Amortized Cost Basis	163
Total amortized cost basis	101,805
Residential and consumer
Credit quality
2020	2,543,705
2019	2,120,213
2018	1,644,201
2017	1,291,172
2016	882,520
Prior	2,236,923
Revolving Loans Amortized Cost Basis	2,516,240
Revolving Loans Converted to Term Loans Amortized Cost Basis	44,123
Total loans and leases		6,282,731
Total amortized cost basis	13,279,097
Residential
Credit quality
Total loans and leases	3,690,218	4,662,175	4,439,618
Residential | Residential mortgage
Credit quality
Total loans and leases		3,768,936
Home equity Line
Credit quality
Total loans and leases	841,624
Home equity Line | Home equity
Credit quality
Total loans and leases		893,239
Consumer
Credit quality
2020	250,019
2019	295,128
2018	226,757
2017	139,788
2016	62,534
Prior	25,576
Revolving Loans Amortized Cost Basis	349,158
Revolving Loans Converted to Term Loans Amortized Cost Basis	4,882
Total loans and leases	1,353,842	1,620,556	1,662,504
Total amortized cost basis	1,353,842
Consumer | 740 and greater
Credit quality
2020	113,373
2019	122,965
2018	99,678
2017	54,691
2016	24,029
Prior	6,034
Revolving Loans Amortized Cost Basis	114,748
Revolving Loans Converted to Term Loans Amortized Cost Basis	275
Total amortized cost basis	535,793
Consumer | 680 - 739
Credit quality
2020	83,316
2019	90,853
2018	66,143
2017	36,426
2016	16,358
Prior	4,985
Revolving Loans Amortized Cost Basis	76,391
Revolving Loans Converted to Term Loans Amortized Cost Basis	773
Total amortized cost basis	375,245
Consumer | 620 - 679
Credit quality
2020	40,469
2019	48,904
2018	33,917
2017	24,705
2016	11,144
Prior	3,788
Revolving Loans Amortized Cost Basis	36,622
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,221
Total amortized cost basis	200,770
Consumer | 550 - 619
Credit quality
2020	9,125
2019	20,274
2018	17,693
2017	15,126
2016	7,825
Prior	2,883
Revolving Loans Amortized Cost Basis	12,980
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,458
Total amortized cost basis	87,364
Consumer | Less than 550
Credit quality
2020	3,017
2019	10,139
2018	9,189
2017	6,517
2016	3,123
Prior	1,118
Revolving Loans Amortized Cost Basis	5,261
Revolving Loans Converted to Term Loans Amortized Cost Basis	799
Total amortized cost basis	39,163
Consumer | No Score
Credit quality
2020	339
2019	103
2018	64
2017	109
2016	10
Revolving Loans Amortized Cost Basis	33,854
Revolving Loans Converted to Term Loans Amortized Cost Basis	356
Total amortized cost basis	34,835
Consumer | Other
Credit quality
2020	380
2019	1,890
2018	73
2017	2,214
2016	45
Prior	6,768
Revolving Loans Amortized Cost Basis	69,302
Total amortized cost basis	80,672
Consumer | Consumer loans
Credit quality
Total loans and leases		226,304
Residential Mortgage.
Credit quality
2020	864,559
2019	482,495
2018	389,725
2017	471,962
2016	391,156
Prior	1,089,580
Revolving Loans Amortized Cost Basis	834,099
Revolving Loans Converted to Term Loans Amortized Cost Basis	8,266
Total amortized cost basis	4,531,842
Home equity line
Credit quality
Revolving Loans Amortized Cost Basis	833,521
Revolving Loans Converted to Term Loans Amortized Cost Basis	8,103
Total amortized cost basis	841,624
Home equity line | 740 and greater
Credit quality
Revolving Loans Amortized Cost Basis	608,282
Revolving Loans Converted to Term Loans Amortized Cost Basis	2,163
Total amortized cost basis	610,445
Home equity line | 680 - 739
Credit quality
Revolving Loans Amortized Cost Basis	159,886
Revolving Loans Converted to Term Loans Amortized Cost Basis	3,155
Total amortized cost basis	163,041
Home equity line | 620 - 679
Credit quality
Revolving Loans Amortized Cost Basis	44,005
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,571
Total amortized cost basis	45,576
Home equity line | 550 - 619
Credit quality
Revolving Loans Amortized Cost Basis	11,644
Revolving Loans Converted to Term Loans Amortized Cost Basis	884
Total amortized cost basis	12,528
Home equity line | Less than 550
Credit quality
Revolving Loans Amortized Cost Basis	5,159
Revolving Loans Converted to Term Loans Amortized Cost Basis	330
Total amortized cost basis	5,489
Home equity line | No Score
Credit quality
Revolving Loans Amortized Cost Basis	4,545
Total amortized cost basis	4,545
Commercial and Industrial
Credit quality
2020	931,522
2019	349,849
2018	215,307
2017	81,113
2016	56,095
Prior	111,069
Revolving Loans Amortized Cost Basis	1,243,900
Revolving Loans Converted to Term Loans Amortized Cost Basis	30,652
Total loans and leases	3,019,507	2,743,242	3,208,760
Total amortized cost basis	3,019,507
Commercial and Industrial | Loans graded
Credit quality
Total loans and leases		2,743,242
Commercial and Industrial | Pass
Credit quality
2020	873,639
2019	324,030
2018	183,329
2017	73,000
2016	49,886
Prior	94,360
Revolving Loans Amortized Cost Basis	1,058,786
Revolving Loans Converted to Term Loans Amortized Cost Basis	28,853
Total loans and leases		2,585,908
Total amortized cost basis	2,685,883
Commercial and Industrial | Special mention
Credit quality
2020	20,937
2019	10,370
2018	20,164
2017	2,099
2016	279
Prior	8,316
Revolving Loans Amortized Cost Basis	101,183
Revolving Loans Converted to Term Loans Amortized Cost Basis	1,549
Total loans and leases		91,365
Total amortized cost basis	164,897
Commercial and Industrial | Substandard
Credit quality
2020	23,804
2019	2,023
2018	2,568
2017	677
2016	4,063
Prior	8,113
Revolving Loans Amortized Cost Basis	33,775
Revolving Loans Converted to Term Loans Amortized Cost Basis	250
Total loans and leases		65,969
Total amortized cost basis	75,273
Commercial and Industrial | Other
Credit quality
2020	13,142
2019	13,426
2018	9,246
2017	5,337
2016	1,867
Prior	280
Revolving Loans Amortized Cost Basis	50,156
Total amortized cost basis	93,454
Commercial real estate
Credit quality
2020	344,374
2019	678,824
2018	586,274
2017	484,627
2016	343,882
Prior	894,258
Revolving Loans Amortized Cost Basis	60,114
Revolving Loans Converted to Term Loans Amortized Cost Basis	323
Total loans and leases	3,392,676	3,463,953	2,990,783
Total amortized cost basis	3,392,676
Commercial real estate | Loans graded
Credit quality
Total loans and leases		3,463,953
Commercial real estate | Pass
Credit quality
2020	342,845
2019	611,243
2018	541,104
2017	447,366
2016	295,426
Prior	814,398
Revolving Loans Amortized Cost Basis	47,604
Revolving Loans Converted to Term Loans Amortized Cost Basis	323
Total loans and leases		3,327,659
Total amortized cost basis	3,100,309
Commercial real estate | Special mention
Credit quality
2020	1,500
2019	63,617
2018	26,187
2017	33,482
2016	37,841
Prior	61,279
Revolving Loans Amortized Cost Basis	2,999
Total loans and leases		106,331
Total amortized cost basis	226,905
Commercial real estate | Substandard
Credit quality
2020	29
2019	3,964
2018	18,983
2017	3,779
2016	10,615
Prior	18,083
Revolving Loans Amortized Cost Basis	9,511
Total loans and leases		29,963
Total amortized cost basis	64,964
Commercial real estate | Other
Credit quality
Prior	498
Total amortized cost basis	498
Construction
Credit quality
2020	70,509
2019	250,631
2018	211,831
2017	94,034
2016	25,492
Prior	54,353
Revolving Loans Amortized Cost Basis	28,969
Total loans and leases	735,819	519,241	626,757
Total amortized cost basis	735,819
Construction | Loans graded
Credit quality
Total loans and leases		519,241
Construction | Pass
Credit quality
2020	53,931
2019	233,730
2018	202,808
2017	83,792
2016	23,171
Prior	41,536
Revolving Loans Amortized Cost Basis	28,386
Total loans and leases		515,993
Total amortized cost basis	667,354
Construction | Special mention
Credit quality
2019	508
2018	707
2017	4,717
Prior	9,172
Total loans and leases		127
Total amortized cost basis	15,104
Construction | Substandard
Credit quality
2018	541
2017	1,840
2016	521
Prior	989
Total loans and leases		3,121
Total amortized cost basis	3,891
Construction | Other
Credit quality
2020	16,578
2019	16,393
2018	7,775
2017	3,685
2016	1,800
Prior	2,656
Revolving Loans Amortized Cost Basis	583
Total amortized cost basis	49,470
Lease financing
Credit quality
2020	82,722
2019	63,286
2018	14,307
2017	19,648
2016	3,361
Prior	62,087
Total loans and leases	245,411	202,483	$ 147,769
Total amortized cost basis	245,411
Lease financing | Loans graded
Credit quality
Total loans and leases		202,483
Lease financing | Pass
Credit quality
2020	79,064
2019	60,717
2018	13,669
2017	17,207
2016	3,010
Prior	61,266
Total loans and leases		201,461
Total amortized cost basis	234,933
Lease financing | Special mention
Credit quality
2020	950
2019	892
2018	311
2017	1,300
2016	351
Prior	295
Total loans and leases		$ 1,022
Total amortized cost basis	4,099
Lease financing | Substandard
Credit quality
2020	2,708
2019	1,677
2018	327
2017	1,141
Prior	526
Total amortized cost basis	6,379
Commercial Lending
Credit quality
2020	1,429,127
2019	1,342,590
2018	1,027,719
2017	679,422
2016	428,830
Prior	1,121,767
Revolving Loans Amortized Cost Basis	1,332,983
Revolving Loans Converted to Term Loans Amortized Cost Basis	30,975
Total amortized cost basis	$ 7,393,413