Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 24,864	$ 26,570
Accumulated Amortization	(10,379)	(10,875)
Net Carrying Amount	14,485	15,695
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	18,659	20,333
Accumulated Amortization	(6,892)	(7,586)
Net Carrying Amount	11,767	12,747
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,699	5,699
Accumulated Amortization	(3,242)	(3,061)
Net Carrying Amount	2,457	2,638
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	506	538
Accumulated Amortization	(245)	(228)
Net Carrying Amount	$ 261	$ 310