Annual percentage of additional shares which equals to the issued and outstanding shares.

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Grantees with more than five years vesting term, percent.

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Increase in common stock capital shares reserved for future issuance.

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Maximum vesting term for more than ten percent grantees.

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Share based compensation arrangement by share based payment award additional annual percentage increase.

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Share-based compensation arrangement by share-based payment award, additional number of shares available for grant.

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Share based compensation arrangement by share based payment award maximum annual fair market value per employee.

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Period from the Plan effective date that the Plan expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Aggregate number of common shares reserved for future issuance.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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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Amount of tax benefit for recognition of expense of award 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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Discount rate from fair value on purchase date that participants pay for shares.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Date the equity-based award expires, in YYYY-MM-DD format.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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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 highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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The highest quantity of shares an employee can purchase under the plan per period.

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Number of shares authorized for issuance under share-based payment arrangement.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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

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Number of options outstanding, including both vested and non-vested options.

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The increase or decrease in number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding, including vested options.

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Number of shares issued 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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Number of options vested.

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

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Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended					12 Months Ended
	Oct. 31, 2018	Jun. 30, 2018	Feb. 28, 2018	Apr. 30, 2016	Mar. 31, 2015	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2021	Jan. 01, 2020	Jan. 01, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding option awards and restricted unit awards						6,607,587,000	5,357,844,000
Tax benefits recognized						$ 0	$ 0	$ 0
Expected dividend yield						0.00%	0.00%	0.00%
Employees and Non-Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expense recognized for unvested employee and non-employee awards						$ 0	$ 0	$ 0
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value						$ 4.96	$ 4.68	$ 8.09
Intrinsic value of options exercised						$ 700,000	$ 400,000	$ 1,000,000.0
Unrecognized stock-based compensation expense for options						$ 15,100,000
Weighted average period over which unrecognized compensation is expected to be recognized						2 years 7 months 6 days
Stock Options \| Non-Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option issued						0	0	0
Stock option vested						0	1,663	0
Restricted Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, granted to employees						0	228,200	0
Unrecognized stock-based compensation expense						$ 1,600,000
Restricted Common Stock \| Non-Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, granted to employees						0	0	0
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grantees with more than five years vesting term, percent					10.00%
Maximum vesting term for more than ten percent grantees					5 years
Number of common stock to option outstanding						136,560
Number of common stock available for issuance				509,869
2015 Equity Incentive Plan \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of market value of common stock					100.00%
2015 Equity Incentive Plan \| Maximum \| Stock option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, expiration period					10 years
2016 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Initial reserves of common stock				1,100,000
Increase in number of shares of common stock reserved for issuance	1,759,602
Share based compensation plan expiration date	Aug. 07, 2028
Annual percentage of additional shares						4.00%
Additional number of shares available for issuance									1,918,363	1,163,377	965,603
Total number of common stock reserved for issuance						8,802,022
Outstanding option awards and restricted unit awards						6,317,069
2018 Equity Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Initial reserves of common stock			1,100,000
Total number of common stock reserved for issuance						1,100,000
Outstanding option awards and restricted unit awards						343,958
2018 Plan, 2016 Plan and 2015 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, expiration period			10 years
2018 Plan, 2016 Plan and 2015 Plan \| Four Year Vesting
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, vesting period			4 years
2018 Plan, 2016 Plan and 2015 Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, vesting period			4 years
2016 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional number of shares available for issuance									479,590	290,844	241,400
Total number of common stock reserved for issuance				165,000		874,923
Percentage of discount through payroll deductions to eligible employees to purchase common stock				15.00%
Percentage of fair market value of common stock				85.00%
Maximum number of shares permitted for per employee				2,000
Maximum purchase value per employee under employee stock purchase plan				$ 25,000
Employee stock purchase plan termination period				10 years
Additional annual percentage increase of common stock		1.00%
Expected dividend yield						0.00%	0.00%	0.00%