Common Stock - Additional Information (Detail) (USD $)
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9 Months Ended | 3 Months Ended | 6 Months Ended | 1 Months Ended | 42 Months Ended | 3 Months Ended | 12 Months Ended | 3 Months Ended | 12 Months Ended | 1 Months Ended | 9 Months Ended | |||
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Sep. 30, 2013
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Sep. 30, 2012
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Mar. 31, 2013
Series A Warrants [Member]
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Jun. 30, 2013
Institutional Investors [Member]
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Jun. 30, 2013
Common Stock [Member]
Institutional Investors [Member]
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Jun. 30, 2009
2009 Sales Agreement [Member]
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Nov. 30, 2012
2009 Sales Agreement [Member]
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Mar. 31, 2013
December 2011 Financing [Member]
Series A Warrants [Member]
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Dec. 31, 2011
December 2011 Financing [Member]
Series A Warrants [Member]
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Mar. 31, 2013
December 2011 Financing [Member]
Common Stock [Member]
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Dec. 31, 2012
December 2011 Financing [Member]
Common Stock [Member]
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Dec. 31, 2012
2012 Amended Sales Agreement [Member]
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Sep. 30, 2013
2012 Amended Sales Agreement [Member]
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Sep. 30, 2013
2012 Amended Sales Agreement [Member]
Common Stock [Member]
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Subsidiary, Sale of Stock [Line Items] | ||||||||||||||
Shares available to sale | $ 30,000,000 | $ 30,000,000 | $ 30,000,000 | |||||||||||
Gross proceeds from common stock | 6,115,442 | 16,196,587 | 3,000,000 | 26,700,000 | 3,317,000 | |||||||||
Percentage of compensation paid to sales agent | 3.00% | |||||||||||||
Common stock, sold | 1,645,639 | 1,733,771 | ||||||||||||
Sale of stock, price per share | $ 1.823 | $ 1.91 | ||||||||||||
Number of warrants exercised | 334,534 | |||||||||||||
Number of shares issued upon warrants exercise | 329,131 | 334,534 | 2,700,000 | |||||||||||
Proceeds from sale of stock | 468,000 | 468,000 | 468,000 | |||||||||||
Exercise period of rights | 3 years | |||||||||||||
Additional amounts of common stock to sell | $ 27,000,000 | |||||||||||||
Warrants termination agreement | 2013-10 |