Stock-Based Compensation - Schedule of Standard and Market-based Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Standard stock options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning outstanding balance (in shares)	3,421,121	3,596,533	3,486,157
Granted (in shares)	489,568	815,794	525,840
Exercised (in shares)	(70,608)	(395,515)	(239,071)
Forfeited (in shares)	(361,687)	(344,541)	(116,425)
Expired (in shares)	(200,403)	(251,150)	(59,968)
Ending outstanding balance (in shares)	3,277,991	3,421,121	3,596,533
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning balance (in dollars per share)	$ 8.44	$ 8.45	$ 8.30
Weighted average exercise price, granted (in dollars per share)	8.48	7.85	10.15
Weighted average exercise price, exercised (in dollars per share)	7.34	6.48	6.82
Weighted average exercise price, forfeited (in dollars per share)	9.11	9.05	12.38
Weighted average exercise price, expired (in dollars per share)	15.04	8.87	13.75
Weighted average exercise price, ending balance (in dollars per share)	7.99	8.44	8.45
Weighted average fair value of options granted (in dollars per share)	$ 3.82	$ 3.67	$ 4.56
Aggregate intrinsic value of options exercised	$ 151	$ 918	$ 1,186
Market condition based stock options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning outstanding balance (in shares)	225,000	200,000	50,000
Granted (in shares)	120,830	75,000	150,000
Exercised (in shares)	0	0	0
Forfeited (in shares)	(73,749)	(50,000)	0
Expired (in shares)	0	0	0
Ending outstanding balance (in shares)	272,081	225,000	200,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning balance (in dollars per share)	$ 8.39	$ 9.05	$ 11,940.00
Weighted average exercise price, granted (in dollars per share)	8.65	9.00	8.09
Weighted average exercise price, exercised (in dollars per share)
Weighted average exercise price, forfeited (in dollars per share)	8.64	11.94
Weighted average exercise price, expired (in dollars per share)
Weighted average exercise price, ending balance (in dollars per share)	8.44	8.39	9.05
Weighted average fair value of options granted (in dollars per share)	$ 3.12	$ 3.68	$ 3.64
Aggregate intrinsic value of options exercised