Description of the Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended				12 Months Ended
	Dec. 31, 2015	May. 31, 2015	Feb. 28, 2014	Jan. 31, 2014	Jun. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subsidiary, Sale of Stock [Line Items]
Place of incorporation						Delaware
Date of incorporation						Jun. 20, 2003
Reverse stock split of common stock and preferred stock						1-for-32
Common stock, shares issued				2,972,972	5,400,000
Common stock price per share	$ 0.0001				$ 10.00	$ 0.0001	$ 0.0001
Preferred stock, shares outstanding	0				0	0
Proceeds from underwritten public offering				$ 55,000		$ 12,518	$ 56,987	$ 46,820
Underwriters partially exercised an overallotment option, additional gross proceeds			$ 6,400			$ 876	$ 411	$ 387
Proceeds from underwritten public offering after fees and commissions			$ 57,000
Cowen And Company, LLC [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued	960,400
Proceeds from underwritten public offering after fees and commissions	$ 12,500
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 the sales agent upon five days' notice.
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%
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued			345,945
At the market equity offering [Member] | Cowen And Company, LLC [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock remained available for sale	$ 27,000					$ 27,000