Stockholders' Equity - Summary of RSUs Activity (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value
Increase in treasury shares (in shares)	15,000	8,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, Number of RSUs, Beginning balance (in shares)	2,737,353
Canceled, Number of RSUs (in shares)	(651,250)
Vested, Number of RSUs (in shares)	(162,481)
Outstanding, Number of RSUs, Ending balance (in shares)	1,923,622
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value
Outstanding, Weighted-Average Grant Date Fair Value, Beginning balance (in dollars per share)	$ 3.83
Canceled, Weighted-Average Grant Date Fair Value (in dollars per share)	3.69
Vested, Weighted-Average Grant Date Fair Value (in dollars per share)	4.10
Outstanding, Weighted-Average Grant Date Fair Value, Ending balance (in dollars per share)	$ 3.85