Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Allowance for loan losses	$ 16,198	$ 15,246	$ 16,386
Compensation and benefits	5,444	6,114	8,764
Security gains and losses	2,854	2,964	2,817
Purchase accounting adjustments		1,275	1,497
Partnership adjustments		1,921	1,158
Non-accrual interest income	2,392	2,254	2,129
Tax credit carryforwards	12,744	13,580	10,163
Federal net operating loss carryforwards	12,020		597
Fair value adjustments on securities available-for-sale	5,394	1,979
Other	5,194	2,264	2,169
Gross deferred tax assets	62,240	47,597	45,680
Deferred tax liabilities:
Depreciation and amortization	(3,448)	(1,530)	(1,900)
Accretion on securities	(421)	(2)	(295)
Fair value adjustments on securities available-for-sale			(2,297)
Purchase accounting adjustments	(149)
Partnership adjustments	(1,128)
Other	(2,519)	(1,511)	(1,728)
Gross deferred tax liabilities	(7,665)	(3,043)	(6,220)
Net deferred tax assets	$ 54,575	$ 44,554	$ 39,460