Covered Loans - Schedule of Accretable Yield, or Income Expected to be Collected (Detail) (Covered Loans [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Covered Loans [Member]
Covered Loans [Line Items]
Balance at January 1	$ 35,742	$ 73,211
Accretion of income	(3,344)	(11,339)
Reclassifications from (to) nonaccretable difference	3,132	13,412
Disposals/other adjustments	129	2,006
Balance at March 31	$ 35,659	$ 77,290