Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 23,632	$ 26,570
Accumulated Amortization	(9,734)	(10,875)
Net Carrying Amount	13,898	15,695
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	17,447	20,333
Accumulated Amortization	(6,151)	(7,586)
Net Carrying Amount	11,296	12,747
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,699	5,699
Accumulated Amortization	(3,331)	(3,061)
Net Carrying Amount	2,368	2,638
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	486	538
Accumulated Amortization	(252)	(228)
Net Carrying Amount	$ 234	$ 310