Notes Payable - Additional Information 2 (Detail) (USD $)
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3 Months Ended | 176 Months Ended | 3 Months Ended | 3 Months Ended | 1 Months Ended | 3 Months Ended | |||||||||
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Mar. 31, 2014
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Mar. 31, 2013
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Mar. 31, 2014
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Mar. 31, 2014
Essex Notes [Member]
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Mar. 31, 2013
Essex Notes [Member]
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Jan. 31, 2014
Essex Notes [Member]
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Dec. 31, 2013
Essex Notes [Member]
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Dec. 20, 2013
Essex Notes [Member]
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Dec. 20, 2013
Essex Notes [Member]
Maximum [Member]
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Mar. 31, 2014
Essex Notes [Member]
Warrants [Member]
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Dec. 31, 2013
Essex Notes [Member]
Short Term [Member]
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Jan. 31, 2014
Essex Notes [Member]
Series E-5 convertible preferred stock [Member]
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Mar. 31, 2014
Hercules Notes Payable [Member]
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Mar. 31, 2013
Hercules Notes Payable [Member]
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Dec. 31, 2013
Hercules Notes Payable [Member]
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Debt Instrument [Line Items] | |||||||||||||||
Secured promissory notes | $ 10,800,000 | ||||||||||||||
Lease period | 3 years | ||||||||||||||
Percentage of original purchase amount of asset at end of lease | 10.00% | ||||||||||||||
Short term notes | 2,500,000 | 2,500,000 | |||||||||||||
Common stock shares purchased | 12,345 | 12,345 | |||||||||||||
Fair value of warrants | 200,000 | ||||||||||||||
Debt issuance cost | 30,000 | 544,000 | |||||||||||||
Interest expense for amortization of warrant | 9,841,000 | 12,624,000 | 79,100,000 | 9,000 | |||||||||||
Unamortized debt discount | 216,000 | 216,000 | 200,000 | 35,000 | 43,000 | ||||||||||
Payment of principal and interest, Notes payable | $ 2,042,000 | $ 1,816,000 | $ 32,038,000 | $ 6,000 | $ 0 | $ 2,300,000 | $ 2,300,000 |