Accounting for Certain Loans Acquired in a Transfer - Amounts of Loans (Parenthetical) (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 15,027	$ 15,054	$ 14,837	$ 14,837	$ 14,226	$ 14,236	$ 14,534
Loans Purchased With Evidence of Credit Deterioration [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ 71		$ 0