Other Real Estate Owned - Summary of Activity in Covered Other Real Estate Owned (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Real Estate Owned, Disclosure of Detailed Components [Abstract]
Beginning balance	$ 45,893	$ 88,273
Loans transferred to other real estate owned	13,650	31,833
Transfer to purchased, non-covered other real estate owned due to loss share expiration	4,771	13,117
Net gains (losses) on sale and write-downs	(5,965)	(16,395)
Sales proceeds	(32,445)	(57,818)
Ending balance	$ 19,907	$ 45,893