Organization, Basis of Presentation and Liquidity - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($) Segment	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segment | Segment	1
Accumulated deficit	$ (430,482)	$ (405,481)
Working capital	25,900
Shareholders' equity	8,389	23,110
Cash and cash equivalents	$ 28,499	$ 31,462	$ 39,984	$ 47,990