Allowance for Credit Losses - Summary of Provision for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Banking and Thrift, Interest [Abstract]
Provision for non-covered loans	$ 4,949	$ 3,710
Provision for covered loans	0	(2,166)
Total provision for loan losses	4,949	1,544
Provision for unfunded letters of credit	(951)	225
Total provision for credit losses	$ 3,998	$ 1,769