Nature of the Business and Basis of Presentation (Details) - USD ($)
$ in Thousands |
|
1 Months Ended |
3 Months Ended |
9 Months Ended |
|
|
|
Jul. 20, 2018 |
Jul. 31, 2018 |
Sep. 30, 2019 |
Jun. 30, 2019 |
Mar. 31, 2019 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
Jan. 01, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
| Sale of Equity |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Net proceeds after deducting underwriting discounts and commissions and other offering costs |
|
|
|
|
|
|
|
|
|
$ 257,866
|
|
|
|
| Net loss |
|
|
$ (47,015)
|
$ (39,390)
|
$ (32,581)
|
$ (26,362)
|
$ (21,239)
|
$ (14,411)
|
$ (118,986)
|
$ (62,012)
|
|
|
|
| Accumulated deficit |
|
|
$ (268,268)
|
|
|
|
|
|
$ (268,268)
|
|
$ (149,282)
|
$ (150,082)
|
$ (60,979)
|
| Common stock |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Sale of Equity |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Shares issued (in shares) |
|
|
|
|
|
12,055,450
|
|
|
|
|
|
|
|
| Conversion of redeemable convertible preferred stock to common stock (in shares) |
51,845,438
|
51,845,438
|
|
|
|
51,845,438
|
|
|
|
|
|
|
|
| IPO |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Sale of Equity |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Shares issued (in shares) |
12,055,450
|
|
|
|
|
|
|
|
|
|
|
|
|
| Net proceeds after deducting underwriting discounts and commissions and other offering costs |
$ 254,300
|
|
|
|
|
|
|
|
|
|
|
|
|
| Conversion of redeemable convertible preferred stock to common stock (in shares) |
|
131,273
|
|
|
|
|
|
|
|
|
|
|
|
| IPO | Common stock |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Sale of Equity |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Shares issued (in shares) |
12,055,450
|
|
|
|
|
|
|
|
|
|
|
|
|
| Overallotment |
|
|
|
|
|
|
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|
|
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|
| Sale of Equity |
|
|
|
|
|
|
|
|
|
|
|
|
|
| Shares issued (in shares) |
1,572,450
|
|
|
|
|
|
|
|
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|
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|