Intangible Assets and Goodwill - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 26,570	$ 19,540
Accumulated Amortization	(10,875)	(8,905)
Net Carrying Amount	15,695	10,635
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	20,333	13,198
Accumulated Amortization	(7,586)	(6,013)
Net Carrying Amount	12,747	7,185
Customer Relationship Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,699	5,699
Accumulated Amortization	(3,061)	(2,699)
Net Carrying Amount	2,638	3,000
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	538	643
Accumulated Amortization	(228)	(193)
Net Carrying Amount	$ 310	$ 450