Income Taxes - Summary of Net Deferred Tax Asset Reported in Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Provision for credit losses	$ 22,500	$ 13,763
Write-downs of other real estate owned	143	181
Deferred compensation	2,325	2,268
Stock-based compensation	1,672	1,514
Investments in partnership interests	4,695	3,677
Other	405	903
Gross deferred tax assets	31,740	22,306
Unrealized net gains on securities	(2,513)	(1,187)
Premium on securities of banks acquired	(144)	(153)
Intangibles	(6,135)	(6,757)
Basis difference related to tax credits	(2,127)	(2,015)
Depreciation	(11,529)	(10,349)
Prepaid expense deducted	(1,208)	(1,000)
Other	(178)	(180)
Gross deferred tax liabilities	(23,834)	(21,641)
Net deferred tax asset	$ 7,906	$ 665