Acquired SJB Assets and FDIC Loss Sharing Asset - Summary of Activity Related to FDIC Loss Sharing Asset (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
FDIC Indemnification Asset [Roll Forward]
Balance, beginning of period	$ 4,764	$ 18,489
FDIC share of additional losses, net of recoveries	342	(81)
Cash paid to (received from) FDIC, net	1,134	(4)
Net amortization	(3,932)	(12,779)
Other reductions, net	(2,009)	(861)
Balance, end of period	$ 299	$ 4,764