Redeemable Preferred Stock (Details) - USD ($)
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1 Months Ended |
3 Months Ended |
6 Months Ended |
12 Months Ended |
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Apr. 05, 2017 |
Dec. 22, 2016 |
May 08, 2013 |
Dec. 31, 2016 |
Sep. 30, 2017 |
Mar. 31, 2017 |
Jun. 30, 2017 |
Dec. 31, 2017 |
Jun. 30, 2018 |
| Redeemable preferred stock |
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| Payments for redemption of preferred stock |
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$ 3,700,000
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| Series C Redeemable Convertible Preferred Stock |
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| Redeemable preferred stock |
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| Shares issued (in shares) |
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2,611
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| Redeemable stock issued, par value (in dollars per share) |
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$ 0.01
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| Redeemable stock issued, stated value (in dollars per share) |
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$ 0.01
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$ 0.01
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| Redeemable convertible Preferred Stock, shares outstanding |
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2,620
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2,620
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| Series C Redeemable Convertible Preferred Stock | Air Liquide |
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| Redeemable preferred stock |
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| Dividend rate |
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8.00%
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| Aggregate purchase price of shares issued |
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$ 248.794
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| Adjusted conversion price per share |
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$ 0.2343
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$ 0.2343
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| Series D Redeemable Convertible Preferred Stock |
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| Redeemable preferred stock |
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| Shares issued (in shares) |
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18,500
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18,500
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| Redeemable stock issued, par value (in dollars per share) |
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$ 0.01
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| Shares of common stock that can be purchased from warrants issued |
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7,381,500
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| Redeemable stock issued, stated value (in dollars per share) |
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$ 0.01
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| Net proceeds from public offering |
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$ 15,600,000
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| Shares redeemed (in shares) |
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3,700
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| Payments for redemption of preferred stock |
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$ 3,700,000
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| Shares issued upon conversion of redeemable stock (in shares) |
9,548,393
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| Conversion price per share |
$ 1.55
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