Allowance for Credit Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 57,491	$ 58,126
Current	13,221,606	13,148,056
Total Accruing Loans and Leases	11,167	13,206,182
Total Non Accruing Loans and Leases		5,468
Total loans and leases	13,279,097	13,211,650	$ 13,076,191
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	26,688	36,228
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	13,621	9,748
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	17,182	12,150
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,815	3,762
Current	3,013,692	2,739,448
Total Accruing Loans and Leases	2,108	2,743,210
Total Non Accruing Loans and Leases		32
Total loans and leases	3,019,507	2,743,242	3,208,760
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,585	1,525
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	604	808
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,626	1,429
Commercial real estate
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,606	3,802
Current	3,389,070	3,460,121
Total Accruing Loans and Leases	882	3,463,923
Total Non Accruing Loans and Leases		30
Total loans and leases	3,392,676	3,463,953	2,990,783
Commercial real estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	75	1,664
Commercial real estate | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,568	1,125
Commercial real estate | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	963	1,013
Construction
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,292	2,367
Current	732,527	516,874
Total Accruing Loans and Leases	93	519,241
Total loans and leases	735,819	519,241	626,757
Construction | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	779
Construction | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	376
Construction | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,137	2,367
Lease financing
Financing Receivable, Recorded Investment, Past Due
Current	245,411	202,483
Total Accruing Loans and Leases		202,483
Total loans and leases	245,411	202,483	147,769
Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due	10,879
Current	3,679,339
Total loans and leases	3,690,218	4,662,175	4,439,618
Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,382
Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	4,125
Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,372
Home equity Line
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,936
Current	834,688
Total Accruing Loans and Leases	4,818
Total loans and leases	841,624
Home equity Line | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,375
Home equity Line | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	743
Home equity Line | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	4,818
Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	26,963	38,104
Current	1,326,879	1,582,452
Total Accruing Loans and Leases	3,266	1,620,556
Total loans and leases	1,353,842	1,620,556	$ 1,662,504
Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	18,492	26,810
Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	5,205	7,022
Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 3,266	4,272
Residential mortgage | Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due		3,731
Current		3,759,799
Total Accruing Loans and Leases		3,763,530
Total Non Accruing Loans and Leases		5,406
Total loans and leases		3,768,936
Residential mortgage | Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		3,258
Residential mortgage | Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		399
Residential mortgage | Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		74
Home equity | Home equity Line
Financing Receivable, Recorded Investment, Past Due
Total Past Due		6,360
Current		886,879
Total Accruing Loans and Leases		893,239
Total loans and leases		893,239
Home equity | Home equity Line | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		2,971
Home equity | Home equity Line | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		394
Home equity | Home equity Line | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due		2,995
Consumer loans | Consumer
Financing Receivable, Recorded Investment, Past Due
Total loans and leases		$ 226,304