Description of Business - Additional Information (Detail) - USD ($) $ in Thousands			9 Months Ended
	Sep. 30, 2015	May. 11, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Subsidiary, Sale of Stock [Line Items]
Place of incorporation			Delaware
Date of incorporation			Jun. 20, 2003
Aggregate proceeds from equity offering program			$ 12,508	$ 0
Deferred offering costs	$ 137		$ 137		$ 0
Cowen And Company, LLC [Member]
Subsidiary, Sale of Stock [Line Items]
Aggregate proceeds from equity offering program	$ 13,000	$ 40,000
Sales agreement termination, description			The Sales Agreement shall automatically terminate upon the issuance and sale of placement shares equaling sales proceeds of $40.0 million and may be terminated earlier by either the Company or Cowen upon five days’ notice.
Common stock, shares issued	960,400
Proceeds from sale after commission and other expenses	$ 12,500
Deferred offering costs	100		$ 100
Cowen And Company, LLC [Member] | At the market equity offering [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock remained available for sale	$ 27,000		$ 27,000
Cowen And Company, LLC [Member] | Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Percentage of commission on gross sales proceeds of common stock		3.00%