Loss Sharing Agreements and FDIC Loss Share Receivable - Schedule of FDIC Loss Share Receivables (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
FDIC Loss Share Receivable [Line Items]
Balance at beginning of period	$ 69,627
Change due to (reversal of) loan loss provision recorded on FDIC covered loans	(1,852)	(4,876)
Amortization	(6,013)	(19,264)
Balance at end of period	60,972
FDIC Loss Share Receivables [Member]
FDIC Loss Share Receivable [Line Items]
Balance at beginning of period	69,627	162,312
Change due to (reversal of) loan loss provision recorded on FDIC covered loans	(1,852)	(4,876)
Amortization	(6,013)	(19,264)
Recoveries payable (submission of reimbursable losses) to the FDIC	(78)	3,055
Changes due to a change in cash flow assumptions on OREO and other changes	(712)	(42)
Balance at end of period	$ 60,972	$ 141,185