Allowance for Credit Losses - Summary of Allowance for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Receivables [Abstract]
Allowance for non-covered loans	$ 101,942		$ 106,547
Allowance for covered loans	1,111		7,070
Total allowance for loan losses	103,053	106,709	113,617	117,444	121,844	130,200
Allowance for unfunded letters of credit	2,544		3,495
Total allowance for credit losses	$ 105,597		$ 117,112