Assets Acquired in FDIC-Assisted Acquisitions - Rollforward of Acquired Loans Deterioration of Credit Quality (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Covered Loans [Line Items]
Balance, beginning of year	$ 25,493	$ 16,698	$ 16,698
Additions due to acquisitions	0	0	0
Balance, end of year	20,741	30,849	25,493
Loans with Deterioration of Credit Quality [Member]
Covered Loans [Line Items]
Balance, beginning of year	217,047	282,737	282,737
Charge-offs, net of recoveries	(8,099)	(30,371)	(35,306)
Additions due to acquisitions	0	0	0
Other (loan payments, transfers, etc.)	(37,487)	(20,777)	(30,384)
Balance, end of year	171,461	231,589	217,047
Loans without Deterioration of Credit Quality [Member]
Covered Loans [Line Items]
Balance, beginning of year	173,190	228,602	228,602
Additions due to acquisitions	0	0	0
Other (loan payments, transfers, etc.)	(31,062)	(42,316)	(55,412)
Balance, end of year	$ 142,128	$ 186,286	$ 173,190