Employee Benefit Plans - Additional Information (Details) $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2019 USD ($) offering_period $ / shares shares	Sep. 30, 2018 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value assumptions, method used	Black-Scholes-Merton option pricing model
Proceeds under the plan \| $	$ 2,662	$ 0
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering period	24 months
Number of offering periods \| offering_period	4
Length of purchase period	6 months
Employee share purchase price percentage	85.00%
Initial offering period start date	Sep. 25, 2018
Initial offering period end date	Nov. 22, 2020
Time-Based Awards \| Equity Incentive Plans \| New Hires
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Time-Based Awards \| Equity Incentive Plans \| Existing Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Maximum \| Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares purchased by employees	261,000
Common Stock \| 2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	8,371,369
Common Stock \| 2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	2,412,453
Number of shares purchased by employees	260,991
Weighted average purchase price \| $ / shares	$ 10.20
Proceeds under the plan \| $	$ 2,700

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