Covered Loans - Summary of FDIC Loss Sharing Asset (Detail) (USD $) In Thousands, unless otherwise specified					9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2014 Adjustments Not Reflected in Income [Member]	Sep. 30, 2013 Adjustments Not Reflected in Income [Member]	Sep. 30, 2014 Adjustments Reflected in Income [Member]	Sep. 30, 2013 Adjustments Reflected in Income [Member]
Covered Loans [Line Items]
Beginning balance	$ 28,000	$ 88,513	$ 91,558	$ 116,624
Cash received from FDIC					(24,814)	(19,415)
(Amortization) accretion							(35,269)	(6,814)
Loan expenses to be reimbursed					1,488	1,469
Higher (lower) loan loss expectations							(13)	115
Write-downs/(gain) on sale of other real estate							(1,634)	1,965
Recovery amounts due to FDIC								(1,243)
Other					(271)	(1,204)		61
Ending balance	$ 28,000	$ 88,513	$ 91,558	$ 116,624