Allowance for Credit Losses - Summary of Allowance for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Receivables [Abstract]
Allowance for non-covered loans	$ 99,639	$ 106,547
Allowance for covered loans	7,070	7,070
Total allowance for loan losses	106,709	113,617	121,844	130,200
Allowance for unfunded letters of credit	2,544	3,495
Total allowance for credit losses	$ 109,253	$ 117,112