Loans and Allowance for Loan Losses - Non-Accrual Loans, Loans Still Accruing and Past Due 90 Days or More and Restructured Loans (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	$ 28,080	$ 27,371	$ 27,175
Troubled debt restructured loans	695	701	973
Purchased Credit Impaired Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans	937	1,256	1,970
Doubtful [Member]
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructured loans	$ 6,073	$ 6,863	$ 8,527