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Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified |
3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | 6 Months Ended | 12 Months Ended | ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2013
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Jun. 30, 2012
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Jun. 30, 2012
Warrant Liabilities [Member]
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Jun. 30, 2013
Warrant Liabilities [Member]
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Dec. 31, 2012
Warrant Liabilities [Member]
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Jun. 30, 2013
Warrant Liabilities [Member]
Minimum [Member]
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Dec. 31, 2012
Warrant Liabilities [Member]
Minimum [Member]
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Jun. 30, 2013
Warrant Liabilities [Member]
Maximum [Member]
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Dec. 31, 2012
Warrant Liabilities [Member]
Maximum [Member]
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Jun. 30, 2013
Recurring [Member]
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Dec. 31, 2012
Recurring [Member]
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Jun. 30, 2013
Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
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Dec. 31, 2012
Recurring [Member]
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
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Jun. 30, 2013
Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
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Dec. 31, 2012
Recurring [Member]
Significant Other Observable Inputs (Level 2) [Member]
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Jun. 30, 2013
Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
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Dec. 31, 2012
Recurring [Member]
Significant Unobservable Inputs (Level 3) [Member]
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| Assets: | |||||||||||||||||||||||||||||||
| Money market funds | $ 47,773 | [1] | $ 37,461 | [1] | $ 47,773 | [1] | $ 37,461 | [1] | $ 0 | [1] | $ 0 | [1] | $ 0 | [1] | $ 0 | [1] | |||||||||||||||
| U.S. treasury securities | 39,987 | [2] | 39,987 | [2] | 0 | [2] | 0 | [2] | |||||||||||||||||||||||
| Foreign exchange options | 297 | [3] | 488 | [3] | 0 | [3] | 0 | [3] | 297 | [3] | 488 | [3] | 0 | [3] | 0 | [3] | |||||||||||||||
| Total | 48,070 | 77,936 | 47,773 | 77,448 | 297 | 488 | 0 | 0 | |||||||||||||||||||||||
| Liabilities: | |||||||||||||||||||||||||||||||
| Contingent warrant liabilities | 29,618 | 15,001 | 0 | 0 | 0 | 0 | 29,618 | 15,001 | |||||||||||||||||||||||
| Fair Value Inputs, Liabilities, Quantitative Information [Line Items] | |||||||||||||||||||||||||||||||
| Expected volatility (in hundredths) | 40.00% | 40.00% | |||||||||||||||||||||||||||||
| Risk-free interest rate (in hundredths) | 0.20% | 0.30% | 0.70% | 0.70% | |||||||||||||||||||||||||||
| Expected term | 1 year 4 months 24 days | 1 year 10 months 24 days | 3 years 8 months 12 days | 4 years 2 months 12 days | |||||||||||||||||||||||||||
| Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] | |||||||||||||||||||||||||||||||
| Balance, beginning of period | 15,001 | ||||||||||||||||||||||||||||||
| Reclassification of contingent warrant liability to equity upon exercise of warrants | (4) | ||||||||||||||||||||||||||||||
| Net increase in fair value of contingent warrant liabilities upon revaluation | 1,800 | 16,500 | 2,200 | 14,621 | |||||||||||||||||||||||||||
| Balance, end of period | $ 29,618 | $ 15,001 | |||||||||||||||||||||||||||||
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