Assets Acquired in FDIC-Assisted Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended	34 Months Ended
	Mar. 31, 2015	Jul. 31, 2012 Acquisition	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Business Combinations [Abstract]
Number of FDIC-assisted acquisitions participation		10
FDIC loss-share receivable	$ 23,312,000		$ 31,351,000	$ 53,181,000	$ 65,441,000
Federal funds purchased and securities sold under agreements to repurchase	16,100,000
Business acquisition, Charge-offs and expenses	14,000,000
Clawback liability	$ 6,800,000		$ 6,200,000	$ 5,200,000