Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 24,883	$ 26,570
Accumulated Amortization	(9,790)	(10,875)
Net Carrying Amount	15,093	15,695
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	18,659	20,333
Accumulated Amortization	(6,402)	(7,586)
Net Carrying Amount	12,257	12,747
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,699	5,699
Accumulated Amortization	(3,151)	(3,061)
Net Carrying Amount	2,548	2,638
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	525	538
Accumulated Amortization	(237)	(228)
Net Carrying Amount	$ 288	$ 310