Securities - Schedule of Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost and Fair Value Debt Securities [Abstract]
Held-to-maturity, Amortized Cost	$ 1,067,967	$ 1,012,930