Share Based Compensation - Schedule of Fair Value of Stock Option Award Granted Estimated on Date of Grant Using the Black-Scholes-Merton Option Pricing Model (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	1.60%	1.40%	1.10%
Weighted average volatility	73.20%	73.00%	64.60%
Expected life (in years)	5 years 1 month 6 days	4 years 3 months 18 days	5 years 7 months 6 days
Weighted average grant date fair value per share of options granted	$ 2.86	$ 3.89	$ 1.47