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Initial offering period end date.

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Initial offering period start date.

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Share based compensation arrangement by share based payment award percentage increase in outstanding shares.

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Share Based Compensation Arrangement By Share Based Payment Award, Purchase Period

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Amount of cash inflow from issuance of shares under share-based payment arrangement. Excludes option exercised.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Description of method used to estimate fair value of award under share-based payment arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Per share weighted-average price paid for shares purchased on open market for issuance under share-based payment arrangement.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Purchase price of common stock expressed as a percentage of its fair value.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Stockholders' Equity and Employee Benefit Plans - Additional Information (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) offering_period $ / shares shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 05, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds under the plan \| $	$ 5,344	$ 0	$ 0
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares purchased by employees	506,000
2018 Equity Incentive Plan \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	7,648,165
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
2018 Employee Stock Purchase Plan \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	2,167,898
Number of shares purchased by employees	505,546
Weighted average purchase price \| $ / shares	$ 10.57
Proceeds under the plan \| $	$ 5,300
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
At-the-Money Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value assumptions, method used	Black-Scholes-Merton Valuation Model	Black-Scholes-Merton Valuation Model
Out-of-the-Money Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value assumptions, method used			Lattice-Binomial Option Valuation Model
Maximum \| Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Maximum \| 2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increases in number of shares available for issuance				12,500,000
Percentage of outstanding shares				5.00%
Maximum \| 2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increases in number of shares available for issuance				5,346,888
Percentage of outstanding shares				1.00%