Other Real Estate Owned - Summary of Activity in Covered Other Real Estate Owned (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Real Estate Owned, Disclosure of Detailed Components [Abstract]
Beginning balance	$ 19,907	$ 45,893	$ 45,893
Loans transferred to other real estate owned	6,534	9,083	13,650
Transfer from covered other real estate owned due to loss-share expiration	(75)		(1,226)
Net gains (losses) on sale and write-downs	(2,758)	(2,613)	(5,965)
Sales proceeds	(10,982)	(13,937)	(32,445)
Ending balance	$ 12,626	$ 38,426	$ 19,907