Activity in Allowance for Losses on Covered Loans (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Valuation Allowance [Line Items]
Balance, beginning of period				$ 31,395	$ 45,481
Provision for (recovery of) losses		$ 895	$ 334	719	341
Transfer to the allowance for losses on non-covered loans	[1]				(2,416)
Balance, end of period		$ 26,649	$ 46,148	26,649	46,148
Covered
Valuation Allowance [Line Items]
Provision for (recovery of) losses				$ (4,746)	$ 3,083

[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.