Stockholders Equity - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Jan. 31, 2015	Nov. 30, 2010	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders Equity Note [Line Items]
Common stock, number of shares issued	14,636,363
Common stock, par value	$ 0.001		$ 0.001	$ 0.001
Public offering, price per share	$ 5.50
Estimated Net proceeds from public offering	$ 75,300,000
Proceeds from common stock sold			$ 75,300,000	$ 18,488,000	$ 61,425,000
Preferred stock, shares issued			0	0
Stockholder Rights Plan
Stockholders Equity Note [Line Items]
Minimum percentage of common stock acquired by stockholders			15.00%
Designated preferred stock for future issuance			250,000
Series C Junior Participating preferred stock
Stockholders Equity Note [Line Items]
Preferred stock, shares issued			0
2010 Warrants
Stockholders Equity Note [Line Items]
Warrants, number of common stock shares		3,700,000
Warrant exercise price		$ 3.20
Warrants exercisable date		May 15, 2011
Exercisable period		5 years
Warrants exercised			3,300,000	2,600,000	200,000
Class of warrants outstanding			0
Cantor | Sales Agreement
Stockholders Equity Note [Line Items]
Common stock, number of shares issued			0	4,300,000
Maximum common stock offering price			$ 70,000,000
Percentage of proceeds payable as compensation to underwriter			2.00%
Proceeds from common stock sold			$ 0	$ 18,600,000
Common stock registered for sale			$ 22,500,000