Warrants to Purchase Convertible Preferred Stock (Details) - USD ($)
$ / shares in Units, $ in Millions |
1 Months Ended |
12 Months Ended |
Jul. 31, 2018 |
May 31, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Warrants to purchase convertible preferred stock |
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| Other expenses |
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$ 2.2
|
$ 0.8
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| IPO |
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| Warrants to purchase convertible preferred stock |
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| Warrants to purchase aggregate |
135,567
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| Issuance of warrants exercise |
131,273
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| Shares withheld to pay exercise price |
4,294
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| Maximum |
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| Warrants to purchase convertible preferred stock |
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| Other income |
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$ 0.1
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| Series A redeemable convertible preferred stock |
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| Warrants to purchase convertible preferred stock |
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| Maximum number of preferred shares can purchase from outstanding warrants |
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133,333
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| Warrants exercisable price |
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$ 0.60
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| Warrants contractual term (in years) |
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10 years
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| Fair value of warrants |
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$ 0.1
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| Series B convertible preferred stock |
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| Warrants to purchase convertible preferred stock |
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| Maximum number of preferred shares can purchase from outstanding warrants |
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2,234
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| Warrants exercisable price |
|
$ 8.39
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| Warrants contractual term (in years) |
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10 years
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| Series B convertible preferred stock | Maximum |
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| Warrants to purchase convertible preferred stock |
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| Fair value of warrants |
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$ 0.1
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