Common Stock, Capital Shares Reserved for Future Issuance, Annual Increase, Percentage of Outstanding Common Stock

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Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period, Achievement Percentage

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercised in Period, Grant Date Fair Value

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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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Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Amount of cost capitalized for 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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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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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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 non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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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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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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Gross number of share options (or share units) granted during the period.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Percentage of vesting of award 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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Per share amount of par value or stated value of stock classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable.

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The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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Equity and Equity Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended	9 Months Ended
	Jun. 01, 2019	Jul. 27, 2017	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jul. 26, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, authorized (in shares)			500,000,000			500,000,000		500,000,000
Common stock, par value (in dollars per share)			$ 0.001			$ 0.001		$ 0.001
Temporary equity, shares authorized (in shares)			10,000,000			10,000,000		10,000,000
Temporary equity, par value (in dollars per share)			$ 0.001			$ 0.001		$ 0.001
Unrecognized stock-based compensation, options			$ 1,232			$ 1,232
Total grant date fair value, options exercised			9,775	$ 6,205		27,640	$ 19,021
Share-based payment expense			11,348	7,510		25,764	19,792
Stock-based compensation capitalized in property and equipment			563	370		1,714	931
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value			$ 21,400	$ 3,426		$ 47,875	17,509
2004 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life						10 years
Award vesting period						4 years
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved (in shares)			22,028,222			22,028,222		19,916,092	7,898,159
Percentage of common stock, outstanding					5.00%
Expected life					10 years
Restricted stock units outstanding (in shares)			3,948,967			3,948,967		5,023,412
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved (in shares)			3,143,346			3,143,346		2,400,256
Employee stock \| 2004 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved (in shares)			0			0
Employee stock \| 2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved (in shares)		1,600,000
Percentage of common stock, outstanding		1.00%
Purchase price of common stock, percentage of market price of common stock						85.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, period for recognition						10 months 13 days
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units outstanding (in shares)			314,999			314,999
Share-based payment expense							(126)
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeited or canceled (in dollars per share)						$ 19.22
Unrecognized compensation expense, period for recognition						2 years 5 months 15 days
Unrecognized stock-based compensation			$ 69,507			$ 69,507
Restricted stock units granted (in shares)						617,728
Restricted stock units outstanding (in shares)			3,948,967			3,948,967		5,023,412
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Achievement percentage of performance conditions						100.00%
Chief Executive Officer \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	150,000
Options granted (in dollars per share)	$ 27.50
Maximum \| 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period						4 years
Maximum \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage						200.00%
Maximum \| Chief Executive Officer \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	300,000
Minimum \| 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period						2 years
Minimum \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage						0.00%
January To December 2018 Awards [Member] \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment expense							(610)
January To December 2019 Awards [Member] \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment expense						$ 1,493	$ 484