Fair Value of Financial Instruments - Summary of Level 3 Inputs to Monte Carlo (Detail)		1 Months Ended	9 Months Ended		12 Months Ended
	Apr. 02, 2014 shares $ / shares	Jan. 24, 2013 shares $ / shares	Sep. 30, 2015 shares $ / shares	Sep. 30, 2014 $ / shares	Dec. 31, 2014 $ / shares	Apr. 01, 2014 $ / shares
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Stock price (in dollars per share)	$ 11.00		$ 2.77	$ 10.98
Estimated stock volatility			78.00%	54.00%
Level 3 | 2018 Notes
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Stock price (in dollars per share)			$ 2.60		$ 2.58
Estimated credit spread			34.60%		24.50%
Estimated stock volatility			55.00%		55.00%
Level 3 | 2019 Notes
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Stock price (in dollars per share)			$ 2.60		$ 2.58
Estimated credit spread			29.00%		29.00%
Estimated stock volatility			55.00%		55.00%
Senior Subordinated Notes | 2018 Notes
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Conversion rate | shares		121.1240	121.1240
Conversion price (in dollars per share)		$ 8.26	$ 8.26
Maturity date of the Notes			Feb. 01, 2018
Maturity of date of early payment feature			Nov. 01, 2016
Senior Subordinated Notes | 2019 Notes
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Conversion rate | shares	75.7576		75.7576
Conversion price (in dollars per share)			$ 13.20			$ 13.20
Maturity date of the Notes			Oct. 01, 2019
Maturity of date of early payment feature			Jan. 01, 2018