Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) (USD $)	6 Months Ended				6 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Aug. 28, 2012 2010 Shelf Registration Statement [Member]	Oct. 28, 2011 2010 Shelf Registration Statement [Member]	Jun. 30, 2013 Maximum [Member]	Jun. 30, 2012 Maximum [Member]	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2012 Minimum [Member]
Summary Of Basis Of Presentation And Significant Accounting Policies [Line Items]
Maximum maturity period of cash and cash equivalent	3 months
Maturity period of certificates of deposit					1 year		3 months
Number of warrants sold in offering			1,200,000	1,523,370
Minimum amortization period of compensation cost on straight line basis	3 years
Maximum amortization period of compensation cost on straight line basis	5 years
Number of options outstanding	3,511,202
Number of options exercisable	2,827,870
Stock option exercise price range, Minimum	$ 0.47	$ 0.69
Stock option exercise price range, Maximum	$ 6.00	$ 6.00
Potentially dilutive warrants to purchase common stock			2.08	1.30	2.08	1.30	1.04	1.04