Aggregate number of common shares reserved for future issuance.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Amount of cost to be recognized for option under share-based payment arrangement.

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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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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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The grant-date intrinsic value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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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Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense, outstanding stock options	$ 24.3
Stock options vested and expected to vest (in shares)	12,900,000
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	15,395,809
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, stock incentive plans, maximum term	10 years
Estimated remaining weighted average period	2 years 1 month 6 days
Weighted average grant date fair value (in USD per share)		$ 6.84	$ 2.48
Stock options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, stock incentive plan, vesting period	3 years
Stock options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, stock incentive plan, vesting period	4 years
Stock-based awards \| 2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)				4,656,320
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated remaining weighted average period	1 year
Unrecognized stock-based compensation expense, unvested restricted stock or RSUs	$ 1.7
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated remaining weighted average period	3 years 1 month 6 days
Unrecognized stock-based compensation expense, unvested restricted stock or RSUs	$ 59.4
Restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, stock incentive plan, vesting period	2 years
Restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, stock incentive plan, vesting period	4 years
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)				1,396,896
Shares available for grant (in shares)	4,620,087
Estimated remaining weighted average period	1 year 8 months 12 days