Goodwill and Intangible Assets - Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets Core deposit intangible, Gross Carrying Amount	$ 7,400
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets Core deposit intangible, Gross Carrying Amount	12,920	$ 8,526
Amortizable intangible assets Core deposit intangible, Accumulated Amortization	$ (5,549)	$ (4,561)