Assets Acquired in FDIC-Assisted Acquisitions - Schedule of Changes in Accretable Discounts Related Acquired Loans (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Business Combinations [Abstract]
Balance, beginning of year	$ 15,578	$ 25,493	$ 25,493
Accretion	(6,251)	(15,432)	(22,188)
Transfer to purchased, non-covered loans due to loss-share expiration	(84)
Transfers between non-accretable and accretable discounts, net	2,817	5,850	12,273
Balance, end of year	$ 12,060	$ 15,911	$ 15,578