Loans and Allowance for Loan and Lease Losses - Nonaccrual Loans and Restructured Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Impaired loans:
Nonaccruing loans	$ 6,683	$ 18,118
Nonaccruing restructured loans	15,101	5,935
Accruing restructured loans	9,862	11,084
Accruing impaired loans	0	0
Total impaired loans	31,646	35,137
Impaired loans less than 90 days delinquent [Member]
Impaired loans:
Total impaired loans	$ 17,066	$ 32,371