Loans and Allowance for Credit Losses - Summary of Loan Classes and Aging of Past Due Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 16,469,463	$ 16,103,651
Nonaccrual Loans	96,536	87,823
30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	16,558	9,869
Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	2,319	1,952
Total Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	115,413	99,644
Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	16,354,050	16,004,007
Commercial and Industrial Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	6,856,243	7,062,074
Nonaccrual Loans	83,445	33,769
Commercial and Industrial Portfolio [Member] \| 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	10,174	4,652
Commercial and Industrial Portfolio [Member] \| Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,281	319
Commercial and Industrial Portfolio [Member] \| Total Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	94,900	38,740
Commercial and Industrial Portfolio [Member] \| Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	6,761,343	7,023,334
Specialty Lending Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	508,431	511,300
Nonaccrual Loans	1,211	19,437
Specialty Lending Portfolio [Member] \| Total Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,211	19,437
Specialty Lending Portfolio [Member] \| Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	507,220	491,863
Commercial Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	6,155,508	5,908,934
Nonaccrual Loans	6,687	28,386
Commercial Real Estate Portfolio [Member] \| 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,036	2,351
Commercial Real Estate Portfolio [Member] \| Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans		225
Commercial Real Estate Portfolio [Member] \| Total Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	7,723	30,962
Commercial Real Estate Portfolio [Member] \| Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	6,147,785	5,877,972
Consumer Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	2,245,699	1,945,494
Nonaccrual Loans	4,631	5,345
Consumer Real Estate Portfolio [Member] \| 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,028	524
Consumer Real Estate Portfolio [Member] \| Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	77
Consumer Real Estate Portfolio [Member] \| Total Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	5,736	5,869
Consumer Real Estate Portfolio [Member] \| Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	2,239,963	1,939,625
Consumer Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	115,505	117,986
Nonaccrual Loans	62	88
Consumer Portfolio [Member] \| 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	2,729	281
Consumer Portfolio [Member] \| Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	42	120
Consumer Portfolio [Member] \| Total Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	2,833	489
Consumer Portfolio [Member] \| Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	112,672	117,497
Credit Cards Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	393,093	366,968
Nonaccrual Loans	500	798
Credit Cards Portfolio [Member] \| 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	1,591	2,061
Credit Cards Portfolio [Member] \| Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	919	1,288
Credit Cards Portfolio [Member] \| Total Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	3,010	4,147
Credit Cards Portfolio [Member] \| Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	390,083	362,821
Leases and Other Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	194,984	190,895
Leases and Other Portfolio [Member] \| Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans	$ 194,984	$ 190,895