Other Real Estate Owned - Summary of Activity in Covered Other Real Estate Owned (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 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	1,230	4,925	13,650
Transfer from covered other real estate owned due to loss share expiration			(1,226)
Net gains (losses) on sale and write-downs	(1,005)	(1,095)	(5,965)
Sales proceeds	(4,043)	(7,087)	(32,445)
Ending balance	$ 16,089	$ 42,636	$ 19,907