Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Loans, principally due to allowance for credit losses	$ 52,583	$ 23,765
Equity-based compensation	6,293	5,809
Accrued expenses	19,878	12,471
Deferred compensation	14,830	14,234
Miscellaneous	6,471	6,499
Total deferred tax assets before valuation allowance	100,055	62,778
Valuation allowance	(3,278)	(2,332)
Total deferred tax assets	96,777	60,446
Deferred tax liabilities:
Net unrealized gain on securities available for sale	(97,434)	(29,668)
Securities	(13,462)	(23)
Land, buildings and equipment	(41,339)	(32,382)
Original issue discount	(1,969)	(2,455)
Partnership investments	(6,948)	(2,091)
Trust preferred securities	(7,538)	(7,833)
Intangibles	(15,215)	(12,503)
Miscellaneous	(8,430)	(3,669)
Total deferred tax liabilities	(192,335)	(90,624)
Net deferred tax liability	$ (95,558)	$ (30,178)