Fair Value Measurement - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 05, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Liabilities measured with fair value		$ 132,144,000		$ 132,144,000
Net operating loss		$ (3,919,000)	$ (1,299,000)	$ (71,901,000)	$ 12,643,000	$ 3,070,000
Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price				10.00%
Estimated net loss				$ 51,400,000
Maximum [Member] | Volatility Assumption [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price				10.00%
Estimated net loss				$ 11,000,000
Maximum [Member] | Transaction Occurring Assumption [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price				10.00%
Estimated net loss				$ 14,700,000
Minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Preferred stock liquidation preference per share		$ 10.00		$ 10.00
Percentage of closing stock price				10.00%
Estimated net loss				$ 54,600,000
Minimum [Member] | Volatility Assumption [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price				10.00%
Estimated net loss				$ 10,400,000
Minimum [Member] | Transaction Occurring Assumption [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of closing stock price				10.00%
Estimated net loss				$ 14,700,000
Redeemable Convertible Preferred Stock [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Capital	$ 600,000,000
Redeemable Convertible preferred stock, shares issued	600,000	600,000		600,000		0
Preferred stock liquidation preference per share	$ 1,000
Preferred stock dividend rate calculated on interest rate	3.00%
Conversion floor price of common stock		$ 1.75		$ 1.75
Redeemable Convertible Preferred Stock [Member] | Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Common stock value per share		$ 2.25		$ 2.25
Redeemable Convertible Preferred Stock [Member] | Minimum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Preferred stock liquidation preference per share	$ 1,000
Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Liabilities measured with fair value						$ 0