Nature of Business, Financial Condition and Basis of Presentation - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Net loss	$ (938)	$ (15,885)	$ (30,066)	$ (49,477)
Deficit accumulated	(292,219)		(292,219)		(262,153)
Cash and cash equivalents	$ 14,010	$ 25,661	$ 14,010	$ 25,661	$ 24,625	$ 66,744