Description of Business - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	May. 11, 2015	Jun. 30, 2015	Jun. 30, 2015
Subsidiary, Sale of Stock [Line Items]
Place of incorporation			Delaware
Date of incorporation			Jun. 20, 2003
Aggregate proceeds from equity offering program			$ 12,518
Deferred offering costs		$ 137	$ 137
Cowen And Company, LLC [Member]
Subsidiary, Sale of Stock [Line Items]
Aggregate proceeds from equity offering program	$ 40,000	$ 13,000
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%