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Stockholders' Equity - Financial Liabilities Subject to Fair Value Measurements (Detail) (USD $)
In Thousands, unless otherwise specified
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Jun. 30, 2013
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Dec. 31, 2012
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August 2008 warrants [Member]
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|
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
$ 4,462
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$ 8,014
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October 2009 warrants [Member]
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
14,193
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11,963
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March 2011 warrants [Member]
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|
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
15,328
|
12,581
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Total common stock warrants [Member]
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|
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
33,983
|
32,558
|
|
Basis of Fair Value Measurements, Level 1 [Member] | August 2008 warrants [Member]
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|
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
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|
Basis of Fair Value Measurements, Level 1 [Member] | October 2009 warrants [Member]
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
|
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|
Basis of Fair Value Measurements, Level 1 [Member] | March 2011 warrants [Member]
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
|
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|
Basis of Fair Value Measurements, Level 1 [Member] | Total common stock warrants [Member]
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| Class of Warrant or Right [Line Items] |
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| Financial liabilities subject to fair value measurements |
|
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Basis of Fair Value Measurements, Level 2 [Member] | August 2008 warrants [Member]
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|
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| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
|
|
|
Basis of Fair Value Measurements, Level 2 [Member] | October 2009 warrants [Member]
|
|
|
| Class of Warrant or Right [Line Items] |
|
|
| Financial liabilities subject to fair value measurements |
|
|
|
Basis of Fair Value Measurements, Level 2 [Member] | March 2011 warrants [Member]
|
|
|
| Class of Warrant or Right [Line Items] |
|
|
| Financial liabilities subject to fair value measurements |
|
|
|
Basis of Fair Value Measurements, Level 2 [Member] | Total common stock warrants [Member]
|
|
|
| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
|
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|
Basis of Fair Value Measurements, Level 3 [Member] | August 2008 warrants [Member]
|
|
|
| Class of Warrant or Right [Line Items] |
|
|
| Financial liabilities subject to fair value measurements |
4,462
|
8,014
|
|
Basis of Fair Value Measurements, Level 3 [Member] | October 2009 warrants [Member]
|
|
|
| Class of Warrant or Right [Line Items] |
|
|
| Financial liabilities subject to fair value measurements |
14,193
|
11,963
|
|
Basis of Fair Value Measurements, Level 3 [Member] | March 2011 warrants [Member]
|
|
|
| Class of Warrant or Right [Line Items] |
|
|
| Financial liabilities subject to fair value measurements |
15,328
|
12,581
|
|
Basis of Fair Value Measurements, Level 3 [Member] | Total common stock warrants [Member]
|
|
|
| Class of Warrant or Right [Line Items] |
|
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| Financial liabilities subject to fair value measurements |
$ 33,983
|
$ 32,558
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