Allowance for Credit Losses - Aging of Analysis of Past Due Loans and Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	$ 13,103,785	$ 13,279,097
Loans and Leases Past Due 90 Days or More and Still Accruing Interest		11,167
30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	24,793	26,688
60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	4,517	13,621
Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	12,064	17,182
Loans and Leases Past Due 90 Days or More and Still Accruing Interest	6,368
Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	41,374	57,491
Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	13,062,411	13,221,606
Commercial and Industrial
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	2,564,547	3,019,507
Loans and Leases Past Due 90 Days or More and Still Accruing Interest		2,108
Commercial and Industrial | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	6,835	2,585
Commercial and Industrial | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	380	604
Commercial and Industrial | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	1,140	2,626
Loans and Leases Past Due 90 Days or More and Still Accruing Interest	494
Commercial and Industrial | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	8,355	5,815
Commercial and Industrial | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	2,556,192	3,013,692
Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3,528,068	3,392,676
Loans and Leases Past Due 90 Days or More and Still Accruing Interest		882
Commercial Real Estate | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	623	75
Commercial Real Estate | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases		2,568
Commercial Real Estate | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	937	963
Commercial Real Estate | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	1,560	3,606
Commercial Real Estate | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3,526,508	3,389,070
Construction
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	853,865	735,819
Loans and Leases Past Due 90 Days or More and Still Accruing Interest		93
Construction | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases		779
Construction | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	202	376
Construction | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	60	2,137
Loans and Leases Past Due 90 Days or More and Still Accruing Interest	60
Construction | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	262	3,292
Construction | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	853,603	732,527
Lease financing
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	242,971	245,411
Lease financing | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	242,971	245,411
Residential mortgage | Residential
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3,821,407	3,690,218
Residential mortgage | Residential | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3,533	3,382
Residential mortgage | Residential | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	1,290	4,125
Residential mortgage | Residential | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	4,113	3,372
Residential mortgage | Residential | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	8,936	10,879
Residential mortgage | Residential | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	3,812,471	3,679,339
Home equity | Home equity Line
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	825,368	841,624
Loans and Leases Past Due 90 Days or More and Still Accruing Interest		4,818
Home equity | Home equity Line | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	1,310	1,375
Home equity | Home equity Line | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	435	743
Home equity | Home equity Line | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	4,680	4,818
Loans and Leases Past Due 90 Days or More and Still Accruing Interest	4,680
Home equity | Home equity Line | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	6,425	6,936
Home equity | Home equity Line | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	818,943	834,688
Consumer loans | Consumer
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	1,267,559	1,353,842
Loans and Leases Past Due 90 Days or More and Still Accruing Interest		3,266
Consumer loans | Consumer | 30 - 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	12,492	18,492
Consumer loans | Consumer | 60 - 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	2,210	5,205
Consumer loans | Consumer | Greater Than or Equal to 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	1,134	3,266
Loans and Leases Past Due 90 Days or More and Still Accruing Interest	1,134
Consumer loans | Consumer | Total Past Due
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	15,836	26,963
Consumer loans | Consumer | Current
Financing Receivable, Recorded Investment, Past Due
Loans and Leases	$ 1,251,723	$ 1,326,879