Loans Held for Sale, Loans and Allowance for Credit Losses - Summary of Aging of Past Due Loans By Segment and Class of Financing Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	$ 91,971	$ 92,671
Current	13,300,220	12,890,984
Total	13,392,191	12,983,655
90+ Days Past Due and Accruing	1,999	1,120
30-59 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	27,306	37,625
60-89 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	14,840	8,713
90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	49,825	46,333
Commercial and Industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	54,317	62,814
Current	7,694,993	7,375,844
Total	7,749,310	7,438,658
90+ Days Past Due and Accruing	37	193
Commercial and Industrial | 30-59 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	6,975	24,859
Commercial and Industrial | 60-89 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	9,259	2,442
Commercial and Industrial | 90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	38,083	35,513
Commercial and Industrial | General C&I
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	34,642	39,443
Current	4,659,472	4,477,573
Total	4,694,114	4,517,016
90+ Days Past Due and Accruing	13	85
Commercial and Industrial | General C&I | 30-59 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	4,903	23,143
Commercial and Industrial | General C&I | 60-89 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	794	1,117
Commercial and Industrial | General C&I | 90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	28,945	15,183
Commercial and Industrial | Energy Sector
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans		8,166
Current	1,480,497	1,411,791
Total	1,480,497	1,419,957
Commercial and Industrial | Energy Sector | 90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans		8,166
Commercial and Industrial | Restaurant Industry
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	15,918	10,524
Current	1,066,684	1,016,897
Total	1,082,602	1,027,421
90+ Days Past Due and Accruing	24	108
Commercial and Industrial | Restaurant Industry | 30-59 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	871	1,219
Commercial and Industrial | Restaurant Industry | 60-89 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	8,413	1,284
Commercial and Industrial | Restaurant Industry | 90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	6,634	8,021
Commercial and Industrial | Healthcare
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	3,757	4,681
Current	488,340	469,583
Total	492,097	474,264
Commercial and Industrial | Healthcare | 30-59 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	1,201	497
Commercial and Industrial | Healthcare | 60-89 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	52	41
Commercial and Industrial | Healthcare | 90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	2,504	4,143
Commercial Real Estate
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	6,993	7,214
Current	2,973,767	2,880,058
Total	2,980,760	2,887,272
90+ Days Past Due and Accruing	2
Commercial Real Estate | Industrial, retail, and other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	5,530	5,742
Current	1,749,350	1,685,952
Total	1,754,880	1,691,694
90+ Days Past Due and Accruing	2
Commercial Real Estate | Multifamily
Financing Receivable Recorded Investment Past Due [Line Items]
Current	692,169	659,902
Total	692,169	659,902
Commercial Real Estate | Office
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	1,463	1,472
Current	532,248	534,204
Total	533,711	535,676
Commercial Real Estate | 30-59 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	2,813	3,607
Commercial Real Estate | 30-59 days past due | Industrial, retail, and other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	2,486	3,354
Commercial Real Estate | 30-59 days past due | Office
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	327	253
Commercial Real Estate | 60-89 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	1,272	133
Commercial Real Estate | 60-89 days past due | Industrial, retail, and other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	1,272	133
Commercial Real Estate | 90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	2,908	3,474
Commercial Real Estate | 90+ days past due | Industrial, retail, and other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	1,772	2,255
Commercial Real Estate | 90+ days past due | Office
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	1,136	1,219
Consumer
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	30,661	22,643
Current	2,631,460	2,635,082
Total	2,662,121	2,657,725
90+ Days Past Due and Accruing	1,960	927
Consumer | Residential Real Estate
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	30,434	22,360
Current	2,545,640	2,545,935
Total	2,576,074	2,568,295
90+ Days Past Due and Accruing	1,960	887
Consumer | Other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	227	283
Current	85,820	89,147
Total	86,047	89,430
90+ Days Past Due and Accruing		40
Consumer | 30-59 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	17,518	9,159
Consumer | 30-59 days past due | Residential Real Estate
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	17,325	8,967
Consumer | 30-59 days past due | Other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	193	192
Consumer | 60-89 days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	4,309	6,138
Consumer | 60-89 days past due | Residential Real Estate
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	4,283	6,101
Consumer | 60-89 days past due | Other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	26	37
Consumer | 90+ days past due
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	8,834	7,346
Consumer | 90+ days past due | Residential Real Estate
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	8,826	7,292
Consumer | 90+ days past due | Other
Financing Receivable Recorded Investment Past Due [Line Items]
Age Analysis of Past-Due Loans	$ 8	$ 54