Loans and the Allowance for Credit Losses - Schedule of Recorded Investment in Loans by Category (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	$ 10,703,312	$ 10,789,233
Loans held for sale	153,520	168,378
Total loans	10,856,832	10,957,611
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	1,598,921	1,681,182
Commercial And Industrial - PPP [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	823,814	726,256
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	5,712,742	5,705,392
Commercial Real Estate [Member] | Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	642,017	668,277
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	5,070,725	5,037,115
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	1,644,422	1,720,961
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	289,395	309,055
Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Total portfolio loans	$ 634,018	$ 646,387