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Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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Mar. 31, 2013
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Mar. 31, 2012
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Dec. 31, 2012
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Warrant Liabilities [Member]
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| Fair Value Inputs, Liabilities, Quantitative Information [Line Items] | |||||||||||
| Expected volatility (in hundredths) | 40.00% | 40.00% | |||||||||
| Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | |||||||||||
| Balance, beginning of period | $ 15,001 | ||||||||||
| Net increase in fair value of contingent warrant liabilities upon revaluation | 12,840 | 14,400 | |||||||||
| Balance, end of period | 27,841 | 15,001 | |||||||||
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Warrant Liabilities [Member] | Minimum [Member]
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| Fair Value Inputs, Liabilities, Quantitative Information [Line Items] | |||||||||||
| Risk-free interest rate (in hundredths) | 0.30% | 0.30% | |||||||||
| Expected term | 1 year 8 months 12 days | 1 year 10 months 24 days | |||||||||
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Warrant Liabilities [Member] | Maximum [Member]
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| Fair Value Inputs, Liabilities, Quantitative Information [Line Items] | |||||||||||
| Risk-free interest rate (in hundredths) | 0.40% | 0.70% | |||||||||
| Expected term | 3 years 10 months 24 days | 4 years 2 months 12 days | |||||||||
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Recurring [Member]
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| Assets: | |||||||||||
| Money market funds | 37,951 | [1] | 37,461 | [1] | |||||||
| U.S. treasury securities | 19,996 | [2] | 39,987 | [2] | |||||||
| Foreign exchange options | 299 | [3] | 488 | [3] | |||||||
| Total | 58,246 | 77,936 | |||||||||
| Liabilities: | |||||||||||
| Contingent warrant liabilities | 27,841 | 15,001 | |||||||||
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Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
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| Assets: | |||||||||||
| Money market funds | 37,951 | [1] | 37,461 | [1] | |||||||
| U.S. treasury securities | 19,996 | [2] | 39,987 | [2] | |||||||
| Foreign exchange options | 0 | [3] | 0 | [3] | |||||||
| Total | 57,947 | 77,448 | |||||||||
| Liabilities: | |||||||||||
| Contingent warrant liabilities | 0 | 0 | |||||||||
|
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
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| Assets: | |||||||||||
| Money market funds | 0 | [1] | 0 | [1] | |||||||
| U.S. treasury securities | 0 | [2] | 0 | [2] | |||||||
| Foreign exchange options | 299 | [3] | 488 | [3] | |||||||
| Total | 299 | 488 | |||||||||
| Liabilities: | |||||||||||
| Contingent warrant liabilities | 0 | 0 | |||||||||
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Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
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| Assets: | |||||||||||
| Money market funds | 0 | [1] | 0 | [1] | |||||||
| U.S. treasury securities | 0 | [2] | 0 | [2] | |||||||
| Foreign exchange options | 0 | [3] | 0 | [3] | |||||||
| Total | 0 | 0 | |||||||||
| Liabilities: | |||||||||||
| Contingent warrant liabilities | $ 27,841 | $ 15,001 | |||||||||
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