Activity in Allowance for Losses on Covered Loans (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Valuation Allowance [Line Items]
Balance, beginning of period				$ 45,481	$ 64,069
(Recovery of) losses on covered loans		$ (9,028)	$ (3,945)	(8,687)	(18,387)
Transfer to the allowance for losses on non-covered loans	[1]			(2,416)
Balance, end of period		$ 37,632	$ 45,682	37,632	45,682
Covered
Valuation Allowance [Line Items]
(Recovery of) losses on covered loans				$ (5,433)	$ (18,387)

[1] Represents the allowance associated with $14.2 million of loans acquired in the Desert Hills transaction that were transferred from covered loans to non-covered loans upon expiration of the related FDIC loss sharing agreement.