Share Based Compensation - Fair Value of PSUs Granted Determined Using Monte Carlo Simulation (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of award (in years)	6 years	6 years	6 years
Volatility	51.70%	53.50%	60.70%
Risk-free interest rate	1.30%	1.30%	1.60%
Expected dividend yield	0.00%	0.00%	0.00%
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing stock price on grant date	$ 1.12	$ 2.18	$ 3.09
Performance period starting price	$ 1.29	$ 2.52	$ 4.08
Term of award (in years)	2 years 6 months 29 days	2 years 7 months 2 days	2 years 7 months 2 days
Volatility	70.10%	60.50%	50.90%
Risk-free interest rate	0.97%	0.83%	0.60%
Expected dividend yield	0.00%	0.00%	0.00%
Fair value per TSR PSU	$ 1.25	$ 1.71	$ 2.64