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Fair Value Measurements (Details) (USD $)
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Aug. 07, 2013
Preferred stock warrants
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Sep. 30, 2013
Measured on a recurring basis
Level 1
Money market funds
|
Dec. 31, 2012
Measured on a recurring basis
Level 1
Money market funds
|
Dec. 31, 2012
Measured on a recurring basis
Level 3
Redeemable preferred stock warrants
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Dec. 31, 2012
Measured on a recurring basis
Total
Redeemable preferred stock warrants
|
Sep. 30, 2013
Measured on a recurring basis
Total
Money market funds
|
Dec. 31, 2012
Measured on a recurring basis
Total
Money market funds
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|---|---|---|---|---|---|---|---|
| Fair Value Measurements | |||||||
| Cash equivalents | $ 79,004,000 | $ 15,554,000 | $ 79,004,000 | $ 15,554,000 | |||
| Other liabilities | 601,000 | 601,000 | |||||
| Aggregate fair value of warrant liability | $ 1,300,000 |