Stock-Based Compensation - Assumptions Used to Compute Share-Based Compensation Costs for Stock Options Granted (Detail) - $ / shares	6 Months Ended					12 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted average grant-date fair value of stock options						$ 0.77	$ 0.57	$ 0.63
Assumptions
Risk-free interest rate (weighted average)	0.11%	0.40%	0.80%	0.40%	0.11%	1.10%	1.20%	0.60%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
Weighted average expected life (years)	6 months	6 months	6 months	6 months	6 months	4 years	4 years	4 years
Volatility (weighted average)	103.80%	109.10%	74.00%	44.00%	45.00%	83.50%	82.90%	68.10%
Forfeiture rate						23.30%	25.50%	11.40%