Automatic annual increase in number of shares reserved for future issuance.

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Common stock capital shares additional number of shares authorized for future issuance reserved for future issuance.

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Date until which automatic annual increase in number of shares reserved for future issuance.

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Effective date from which automatic annual increase in number of shares reserved for future issuance.

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Number of offering periods.

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Percentage of automatic annual increase in number of shares reserved for future issuance.

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- Definition

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

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- Definition

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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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 equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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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 weighted average fair value at grant date for nonvested equity-based awards issued 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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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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- Definition

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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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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- Definition

An excess of the fair value of the modified award over the fair value of the award immediately before the modification.

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Expected term of 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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- Definition

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

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Number of share options (or share units) exercised during the current period.

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Stock-Based Awards - Additional Information (Details)			12 Months Ended
Stock-Based Awards - Additional Information (Details)	Jan. 01, 2020 shares	Sep. 21, 2017 shares	Dec. 31, 2019 USD ($) offering_period $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offering periods \| offering_period			0
Intrinsic value of stock options exercised \| $			$ 53,200,000	$ 4,400,000
Exercised (in shares)			1,504,583		0
Weighted average grant-date fair value per share of options granted (in dollars per share) \| $ / shares			$ 19.22	$ 19.68	$ 7.63
Unrecognized compensation cost related to unvested share-based awards \| $			$ 60,800,000
Unrecognized compensation cost related to unvested share-based awards, period for recognition			2 years 8 months 12 days
Expenses incurred \| $			$ 20,410,000	$ 9,688,000	$ 4,866,000
President And Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense \| $			$ 2,400,000
Time-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, granted (in shares)			87,000
Weighted average grant date fair value, granted (in dollars per share) \| $ / shares			$ 29.03
Fair-value of units \| $			$ 500,000
Vested (in shares)			12,500	0	0
Forfeited (in shares)			0
Expenses incurred \| $			$ 1,082,000	$ 110,000	$ 0
Time-based restricted stock units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, vesting period			4 years	4 years
Time-based restricted stock units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, vesting period			1 year	1 year
Performance-based restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units, granted (in shares)			57,400
Weighted average grant date fair value, granted (in dollars per share) \| $ / shares			$ 34.43
Vested (in shares)			0	0
Forfeited (in shares)			0
Expenses incurred \| $			$ 0
2015 Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of common stock			100.00%
Expected term (in years)			10 years
2015 Equity Incentive Plan \| Employees and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation, vesting period			4 years
Common Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercised (in shares)			1,508,448	140,074
Common Shares \| 2017 Stock Option and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares reserved for issuance (in shares)		2,655,831	994,282
Effective date from which automatic annual increase in number of shares reserved for future issuance		Jan. 01, 2018
Percentage of automatic annual increase in number of shares reserved for future issuance		4.00%
Common Shares \| 2017 Stock Option and Incentive Plan \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance (in shares)	2,064,706
Common Shares \| 2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares reserved for issuance (in shares)		306,750	1,009,433
Effective date from which automatic annual increase in number of shares reserved for future issuance		Jan. 01, 2018
Date until which automatic annual increase in number of shares reserved for future issuance		Jan. 01, 2027
Automatic annual increase in number of shares reserved for future issuance (in shares)		400,000
Common Shares \| 2017 Employee Stock Purchase Plan \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance (in shares)	400,000
Common Shares \| 2017 Employee Stock Purchase Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of automatic annual increase in number of shares reserved for future issuance		1.00%