Other Operating Expenses - Summary of Other Operating Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Other Income and Expenses [Abstract]
Salaries and employee benefits	$ 22,646	$ 18,831	$ 45,243	$ 36,520
Net occupancy and equipment	7,344	5,707	14,635	10,751
Other operating expenses:
Postage and supplies	1,014	852	1,929	1,623
Advertising and public relations	586	636	1,169	1,036
Telecommunication services	1,616	1,191	2,964	2,207
Professional and outside services	2,526	2,353	6,912	4,526
Software and data processing	766	1,662	1,515	2,799
Travel and meals	821	629	1,617	1,169
FDIC insurance	900	555	1,650	1,105
FDIC and state assessments	331	218	641	431
ATM expense	543	307	1,251	516
Loan collection and repossession expense	1,020	1,528	2,753	1,987
Writedowns of foreclosed and other assets	235	798	2,427	877
Amortization of intangibles	1,640	1,119	3,236	1,932
FHLB prepayment penalty	0	0	2,480	0
Other	1,736	1,492	3,486	7,854
Total non-interest expense	$ 43,724	$ 37,878	$ 93,908	$ 75,333