Stockholders' Equity - Additional Information (Detail) (USD $)
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1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 48 Months Ended | 80 Months Ended | 9 Months Ended | 12 Months Ended | 48 Months Ended | 1 Months Ended | 48 Months Ended | 0 Months Ended | |||||||||||||
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Aug. 31, 2013
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Dec. 31, 2013
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Mar. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2012
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Aug. 02, 2013
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Dec. 31, 2013
Research and development expense [Member]
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Dec. 31, 2012
Research and development expense [Member]
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Dec. 31, 2013
General and administrative expense [Member]
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Dec. 31, 2012
General and administrative expense [Member]
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Dec. 31, 2012
Restricted stock [Member]
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Dec. 31, 2013
Restricted stock [Member]
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Dec. 31, 2012
Restricted stock [Member]
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Dec. 31, 2011
Restricted stock [Member]
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Dec. 31, 2013
Restricted stock [Member]
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Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]
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Dec. 31, 2013
Equity Incentive Plan 2008 [Member]
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Mar. 31, 2012
Equity Incentive Plan 2008 [Member]
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Dec. 31, 2011
Equity Incentive Plan 2008 [Member]
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Aug. 31, 2013
Equity Incentive Plan 2012 [Member]
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Jan. 31, 2012
Equity Incentive Plan 2012 [Member]
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Nov. 30, 2013
Equity Distribution Agreement [Member]
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Dec. 31, 2011
Other Plan [Member]
Restricted stock [Member]
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Aug. 02, 2013
Underwriting Agreement [Member]
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Jul. 17, 2013
Underwriting Agreement [Member]
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Aug. 02, 2013
Underwriting Agreement [Member]
Over Allotment Option Exercised [Member]
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Class of Stock [Line Items] | ||||||||||||||||||||||||||||
Shares authorized under shelf registration statement | 150,000,000 | 150,000,000 | 150,000,000 | 100,000,000 | ||||||||||||||||||||||||
Issuance of common stock | 77,424,956 | 64,686,919 | 77,424,956 | 10,350,000 | 1,350,000 | |||||||||||||||||||||||
Offering price per share | $ 4.50 | $ 4.23 | ||||||||||||||||||||||||||
Proceeds from issuance of common stock | $ 43,400,000 | |||||||||||||||||||||||||||
Underwriting discounts and commissions and other offering expenses | 3,200,000 | |||||||||||||||||||||||||||
Common stock issued through investment bank | 10,350,000 | 4,000,000 | ||||||||||||||||||||||||||
Number of shares issuable upon exercise of warrant | 533,533 | 11,612,791 | 2,404,519 | 13,423,622 | ||||||||||||||||||||||||
Common shares authorized to be issued | 1,521,584 | 5,000,000 | 6,553,986 | |||||||||||||||||||||||||
Shares issued during the year | 0 | 0 | ||||||||||||||||||||||||||
Termination date of Equity Incentive Plan | Jul. 01, 2018 | |||||||||||||||||||||||||||
Restricted common stock to founders | 1,258,934 | 1,086,662 | 172,272 | |||||||||||||||||||||||||
Shares available for issuance | 11,553,986 | |||||||||||||||||||||||||||
Termination date of Equity Incentive Plan | 10 years | |||||||||||||||||||||||||||
Restricted stock issued | 1,380,000 | 1,380,000 | ||||||||||||||||||||||||||
Issuance restricted Common stock to certain employees, advisors and consultants | 55,000 | 60,000 | 1,380,000 | 60,000 | ||||||||||||||||||||||||
Restricted stock cancelled | 3,703 | 9,021 | 164,243 | 89,674 | ||||||||||||||||||||||||
Restricted stock units vested during the period | 8,750 | 21,250 | 305,000 | 211,250 | ||||||||||||||||||||||||
Total employee stock-based compensation recorded as operating expenses | 12,000 | 82,000 | 669,000 | 750,000 | 681,000 | 834,000 | 1,837,000 | |||||||||||||||||||||
Unrecognized stock-based compensation expense | $ 883,000 | $ 883,000 | ||||||||||||||||||||||||||
Unrecognized stock-based compensation expense recognition maximum weighted average period | 1 year 8 months 12 days |