Loans and Allowance for Loan Losses - Summary of Nonperforming and Restructured Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Summary Of Nonperforming And Restructured Assets [Abstract]
Past due 90 days or more and still accruing	$ 2,061	$ 1,135
Nonaccrual	30,321	16,410
Restructured	15,386	16,515
Total nonperforming and restructured loans	47,768	34,060
Other real estate owned and repossessed assets	7,863	8,079
Total nonperforming and restructured assets	$ 55,631	$ 42,139