Other Real Estate Owned - Summary of Activity in Purchased Non-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, January 1	$ 15,585	$ 15,585	$ 15,585
Loans transferred to other real estate owned	2,039	1,425	4,160
Acquired in acquisitions	2,189	11,464	8,864
Transfer from covered other real estate owned due to loss-share expiration	75		1,226
Net gains (losses) on sale and write-downs	182	61	828
Sales proceeds	(6,958)	(628)	(3,769)
Ending balance	$ 13,112	$ 16,598	$ 15,585