Allowance for Credit Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment, Past Due
Total Past Due	$ 100,233	$ 58,126
Current	13,280,037	13,148,056
Total Accruing Loans and Leases		13,206,182
Total Non Accruing Loans and Leases		5,468
Total loans and leases	13,380,270	13,211,650
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	70,421	36,228
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	13,854	9,748
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	15,958	12,150
Total Accruing Loans and Leases	10,913
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Total Past Due	11,685	3,762
Current	3,013,660	2,739,448
Total Accruing Loans and Leases		2,743,210
Total Non Accruing Loans and Leases		32
Total loans and leases	3,025,345	2,743,242
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,634	1,525
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,010	808
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	4,041	1,429
Total Accruing Loans and Leases	4,007
Commercial real estate
Financing Receivable, Recorded Investment, Past Due
Total Past Due	17,667	3,802
Current	3,395,347	3,460,121
Total Accruing Loans and Leases		3,463,923
Total Non Accruing Loans and Leases		30
Total loans and leases	3,413,014	3,463,953
Commercial real estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	14,204	1,664
Commercial real estate | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,706	1,125
Commercial real estate | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	757	1,013
Total Accruing Loans and Leases	757
Construction
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,677	2,367
Current	563,385	516,874
Total Accruing Loans and Leases		519,241
Total loans and leases	572,062	519,241
Construction | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,003
Construction | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	104
Construction | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,570	2,367
Total Accruing Loans and Leases	148
Lease financing
Financing Receivable, Recorded Investment, Past Due
Current	236,623	202,483
Total Accruing Loans and Leases		202,483
Total loans and leases	236,623	202,483
Residential
Financing Receivable, Recorded Investment, Past Due
Total loans and leases		4,662,175
Consumer
Financing Receivable, Recorded Investment, Past Due
Total loans and leases	1,568,073	1,620,556
Residential mortgage | Residential
Financing Receivable, Recorded Investment, Past Due
Total Past Due	8,576	3,731
Current	3,664,879	3,759,799
Total Accruing Loans and Leases		3,763,530
Total Non Accruing Loans and Leases		5,406
Total loans and leases	3,673,455	3,768,936
Residential mortgage | Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,556	3,258
Residential mortgage | Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,349	399
Residential mortgage | Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,671	74
Total Accruing Loans and Leases	82
Home equity | Home equity Line
Financing Receivable, Recorded Investment, Past Due
Total Past Due	10,975	6,360
Current	880,723	886,879
Total Accruing Loans and Leases		893,239
Total loans and leases	891,698	893,239
Home equity | Home equity Line | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,947	2,971
Home equity | Home equity Line | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	1,462	394
Home equity | Home equity Line | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	2,566	2,995
Total Accruing Loans and Leases	2,566
Consumer loans | Consumer
Financing Receivable, Recorded Investment, Past Due
Total Past Due	42,653	38,104
Current	1,525,420	1,582,452
Total Accruing Loans and Leases		1,620,556
Total loans and leases	1,568,073	1,620,556
Consumer loans | Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	33,077	26,810
Consumer loans | Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	6,223	7,022
Consumer loans | Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Total Past Due	3,353	$ 4,272
Total Accruing Loans and Leases	$ 3,353