Loans - Schedule of Purchased Credit Impaired Loans for which Payments Would Not be Collected (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable Impaired [Line Items]
Allowance for loan losses	$ 18,970	$ 19,087	$ 16,903	$ 17,712
Purchased Credit Impaired Loans [Member]
Financing Receivable Impaired [Line Items]
Allowance for loan losses	$ 0