Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 23,611	$ 23,619
Accumulated Amortization	(10,843)	(10,289)
Net Carrying Amount	12,768	13,330
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	17,447	17,447
Accumulated Amortization	(7,071)	(6,611)
Net Carrying Amount	10,376	10,836
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,699	5,699
Accumulated Amortization	(3,506)	(3,419)
Net Carrying Amount	2,193	2,280
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	465	473
Accumulated Amortization	(266)	(259)
Net Carrying Amount	$ 199	$ 214