Loans and Allowance for Credit Losses - Summary of Loan Classes and Aging of Past Due Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 78,909	$ 99,644
Nonaccrual Loans	58,219	87,823
Current	16,831,881	16,004,007
Total Loans	16,910,790	16,103,651
30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	19,425	9,869
Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,265	1,952
Commercial and Industrial Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	37,608	38,740
Nonaccrual Loans	20,724	33,769
Current	7,347,085	7,023,334
Total Loans	7,384,693	7,062,074
Commercial and Industrial Portfolio [Member] | 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	16,884	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 Past Due		319
Specialty Lending Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	16,999	19,437
Nonaccrual Loans	16,999	19,437
Current	465,399	491,863
Total Loans	482,398	511,300
Commercial Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	15,992	30,962
Nonaccrual Loans	15,067	28,386
Current	6,230,376	5,877,972
Total Loans	6,246,368	5,908,934
Commercial Real Estate Portfolio [Member] | 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	794	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 Past Due	131	225
Consumer Real Estate Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	5,080	5,869
Nonaccrual Loans	4,731	5,345
Current	2,133,716	1,939,625
Total Loans	2,138,796	1,945,494
Consumer Real Estate Portfolio [Member] | 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	349	524
Consumer Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	226	489
Nonaccrual Loans	92	88
Current	110,104	117,497
Total Loans	110,330	117,986
Consumer Portfolio [Member] | 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	51	281
Consumer Portfolio [Member] | Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	83	120
Credit Cards Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,004	4,147
Nonaccrual Loans	606	798
Current	366,024	362,821
Total Loans	369,028	366,968
Credit Cards Portfolio [Member] | 30-89 Days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,347	2,061
Credit Cards Portfolio [Member] | Greater than 90 days Past Due and Accruing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,051	1,288
Leases and Other Portfolio [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	179,177	190,895
Total Loans	$ 179,177	$ 190,895