Assets Acquired in FDIC-Assisted Acquisitions - Loan-by-Loan Basis Performance of Fair Value Adjustments (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Business Combinations [Abstract]
Adjustments needed where the Company's initial estimate of cash flows were underestimated: (recorded with a reclassification from non-accretable difference to accretable discount to be accreted into income over remaining term of the loan)	$ 16,070	$ 50,703	$ 51,003
Adjustments needed where the Company's initial estimate of cash flows were overstated: (recorded through a provision for loan losses)	3,425	6,305	7,695
Adjustments needed where the Company's initial estimate of cash flows were underestimated: (recorded with a reclassification from non-accretable difference to accretable discount to be accreted into income over remaining term of the loan)	3,214	10,141	10,201
Adjustments needed where the Company's initial estimate of cash flows were overstated: (recorded through a provision for loan losses)	$ 685	$ 1,261	$ 1,539