Loans and the Allowance for Credit Losses - Schedule of Recorded Investment in Loans by Category (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	$ 10,357,192	$ 10,789,233
Loans held for sale	41,461	168,378
Total loans	10,398,653	10,957,611
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	1,575,612	1,681,182
Commercial And Industrial - PPP [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	543,574	726,256
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	5,705,246	5,705,392
Commercial Real Estate [Member] | Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	588,218	668,277
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	5,117,028	5,037,115
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	1,625,632	1,720,961
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	276,069	309,055
Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	$ 631,059	$ 646,387