Loans - Changes in Accretable Yield for Covered Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance, beginning of period	$ 282,101	$ 122,342	$ 336,208	$ 223,799
Accretion	(24,814)	(15,538)	(78,921)	(46,981)
Net decrease in expected cash flows	0	0	0	(70,014)
Balance, end of period	$ 257,287	$ 106,804	$ 257,287	$ 106,804