Allowance for Credit Losses - Summary of Provision for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Banking and Thrift, Interest [Abstract]
Provision for non-covered loans	$ 0	$ 2,746	$ 4,949	$ 6,456
Provision for covered loans	(5,671)	(110)	(5,671)	(2,276)
Total provision for loan losses	(5,671)	2,636	(722)	4,180
Provision for unfunded letters of credit	0	(84)	(951)	141
Total provision for credit losses	$ (5,671)	$ 2,552	$ (1,673)	$ 4,321