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Stockholders' Equity (Deficit) - Additional Information (Detail) (USD $)
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3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2014
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Sep. 30, 2014
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Sep. 30, 2014
Cashless Exercise of Warrants
Warrants
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Sep. 30, 2014
Cashless Exercise of Warrants
Warrants
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Sep. 30, 2014
Warrants Exercised For Cash
Warrants
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Sep. 30, 2014
October 2009 Offering
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Dec. 31, 2013
October 2009 Offering
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Sep. 30, 2014
October 2009 Offering
Warrants
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Sep. 30, 2014
October 2009 Offering
Warrants
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Sep. 30, 2014
March 2011 Offering
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Dec. 31, 2013
March 2011 Offering
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Sep. 30, 2014
March 2011 Offering
Warrants
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Sep. 30, 2014
March 2011 Offering
Warrants
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| Class Of Warrant Or Right [Line Items] | |||||||||||||
| Warrants exercised | 1,478,528 | 1,478,528 | 2,160,206 | ||||||||||
| Stock issued for warrants exercised | 821,753 | 821,753 | 2,160,206 | ||||||||||
| Net proceeds from warrant exercised | $ 4,400,000 | ||||||||||||
| Reclassification of fair value from liability to permanent equity of warrants exercised | 9,076,000 | 9,076,000 | |||||||||||
| Warrants outstanding | 4,600,000 | 4,600,000 | 649,206 | 4,287,940 | 3,993,783 | 3,993,783 | |||||||
| Warrants exercise price | $ 2.05 | $ 2.05 | $ 2.46 | $ 2.46 | |||||||||
| Warrants expiration date | Oct. 05, 2014 | ||||||||||||
| Change in fair value of common stock warrants | $ (7,781,000) | $ 1,900,000 | $ (1,200,000) | $ (1,600,000) | $ (6,600,000) | ||||||||