The maximum value of award or purchase a plan participant can receive under the plan per period.

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Describes the expected annual number of plan offering periods as determined by the compensation committee.

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Describes the expected term of the offering period as determined by the compensation committee.

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The floor for the equity price in relation to the fair market value of common stock on the date of grant or offering, represented as a percentage.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

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Amount of expense recognized from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments), awarded to key employees or individuals. Excludes amount related to plans that cover generally all employees (for example, but not limited to, qualified pension plans).

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The cash inflow associated with the amount received from the stock plan during the period.

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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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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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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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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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Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

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Number of shares purchased 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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Number of options vested.

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Stock-Based Compensation (Details)	1 Months Ended	3 Months Ended	6 Months Ended				12 Months Ended
Stock-Based Compensation (Details)	Jun. 30, 2017 shares	Sep. 30, 2019 shares	Oct. 31, 2019 USD ($) shares	Apr. 30, 2019 USD ($) shares	Oct. 31, 2018 USD ($) shares	Apr. 30, 2018 USD ($) shares	Dec. 31, 2019 USD ($) period shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	May 31, 2019 shares	Mar. 31, 2019 shares	Jan. 31, 2019 shares	Jun. 30, 2015 shares
2015 Plan
Stock Based Compensation
Shares reserved for issuance							14,062,396						3,451,495
Shares reserved for issuance as a proportion common stock outstanding (as a percent)							4.00%
2015 Plan \| Minimum
Stock Based Compensation
Shares reserved for issuance							3,500,000
Employee stock purchase plan
Stock Based Compensation
Shares reserved for issuance							1,638,280						893,548
Shares reserved for issuance as a proportion common stock outstanding (as a percent)							1.00%
Price in relation to fair market value of common stock on the date of grant, lower range limit (as a percent)							85.00%
Maximum number of shares a participant may receive during the period (in shares)							5,000
Maximum amount of award or purchase during a calendar year \| $							$ 25,000
Maximum offering period, term							27 months
Number of expected offering periods each year \| period							2
Offering period, expected term							6 months
Number of Shares Purchased			136,084	132,177	184,825	206,447
Total Proceeds \| $			$ 2,176,000	$ 2,147,000	$ 1,763,000	$ 1,855,000
Maximum employee contribution of employee's cash compensation (as a percent)							15.00%
Employee stock purchase plan \| Minimum
Stock Based Compensation
Shares reserved for issuance							880,000
Performance-based awards \| Executive Chairman
Stock Based Compensation
Shares approved	425,000							600,000
Compensation expense associated with performance-based awards \| $							$ 3,300,000
Performance-based awards \| Chief Executive Officer
Stock Based Compensation
Shares approved												200,000
Compensation expense associated with performance-based awards \| $							600,000
Performance-based awards \| First Vesting Milestone \| Executive Chairman
Stock Based Compensation
Number of options vested	50,000
Vesting period	1 year
Performance-based awards \| Second Vesting Milestone \| Executive Chairman
Stock Based Compensation
Number of options vested	75,000
Vesting period	1 year
Performance-based awards \| Third Vesting Milestone \| Executive Chairman
Stock Based Compensation
Number of options vested	75,000
Vesting period	1 year
Employee and non-employee stock options
Stock Based Compensation
Stock-based compensation expense \| $							$ 28,624,000	$ 14,198,000	$ 11,402,000
Shares available for issuance							6,416,000	5,431,000
Employee and non-employee stock options \| Executive Chairman
Stock Based Compensation
Shares approved	200,000
Compensation expense associated with performance-based awards \| $							$ 600,000	$ 400,000	$ 0
Employee and non-employee stock options \| Chief Executive Officer
Stock Based Compensation
Number of options vested		37,500
Employee and non-employee stock options \| 2015 Plan
Stock Based Compensation
Vesting period							4 years
Expiration period							10 years
Stock appreciation rights \| 2015 Plan
Stock Based Compensation
Expiration period							10 years
Restricted stock units
Stock Based Compensation
Number of shares vested							541
Shares granted							2,019
Restricted stock units \| Chief Executive Officer
Stock Based Compensation
Shares approved												100,000
Number of shares vested		18,750
Restricted stock units \| Chief Financial Officer
Stock Based Compensation
Shares approved											100,000
Number of shares vested		25,000
Restricted stock units \| Chief Operating Officer
Stock Based Compensation
Shares approved											100,000
Number of shares vested		25,000
Restricted stock units \| Chief Financial Officer and Chief Operating Officer
Stock Based Compensation
Compensation expense associated with performance-based awards \| $							$ 1,200,000
Restricted stock units \| Employees
Stock Based Compensation
Shares approved										188,099
Compensation expense associated with performance-based awards \| $							1,300,000
Restricted stock units \| Senior VP of Business Development
Stock Based Compensation
Shares approved		50,000
Compensation expense associated with performance-based awards \| $							$ 300,000