Stock-Based Compensation - Summary of Outstanding and Exercisable Stock Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares Under Options, Outstanding, Beginning balance	1,005,836
Number of Shares Under Options, Granted	0
Number of Shares Under Options, Exercised	0
Number of Shares Under Options, Forfeited	(190,501)
Number of Shares Under Options, Outstanding, Ending balance	815,335	1,005,836
Number of Shares Under Options, Exercisable	815,335
Number of Shares Under Options, Vested or expected to vest	815,335
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 24.07
Weighted Average Exercise Price, Granted	0
Weighted Average Exercise Price, Exercised	0
Weighted Average Exercise Price, Forfeited	26.03
Weighted Average Exercise Price, Outstanding, Ending balance	23.61	$ 24.07
Weighted Average Exercise Price, Exercisable	23.61
Weighted Average Exercise Price, Vested or expected to vest	$ 23.61
Remaining Contractual Life In Years, Outstanding	3 years 3 months 18 days	4 years 2 months 12 days
Remaining Contractual Life In Years, Exercisable	3 years 3 months 18 days
Remaining Contractual Life In Years, Vested or expected to vest	3 years 3 months 18 days
Intrinsic Value, Outstanding, Beginning balance	$ 0
Intrinsic Value, Outstanding, Ending balance	0	$ 0
Intrinsic Value, Exercisable	0
Intrinsic Value, Vested or expected to vest	$ 0