Business combination estimated post combination expense.

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Number of equal vesting installments.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Aggregate number of common shares reserved for future issuance.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of liabilities classified as other, due within one year or the normal operating cycle, if longer.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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No definition available.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

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 (Detail) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($)	Dec. 31, 2018 USD ($) Installment $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Sep. 27, 2017 shares	Dec. 31, 2012 shares	Dec. 31, 2001 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Business combination, estimated post combination expense	$ 2,000
Other accrued expenses and current liabilities		$ 26,347	$ 21,744
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total requisite service period of awards		4 years
Business combination, estimated post combination expense		$ 3,400
Weighted average remaining service period		2 years
Other accrued expenses and current liabilities		$ 600
Liability for Class A Redeemable Common Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Financial liabilities				$ 10,632
NSO Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, outstanding \| shares		4,337,856	6,441,972
Exercise price stock options outstanding \| $ / shares		$ 0.000025	$ 0.000025
Contractual term		35 years
ISO Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, outstanding \| shares		532,220	888,864
Exercise price stock options outstanding \| $ / shares			$ 0.67
Contractual term		10 years
Intrinsic value of options exercised		$ 5,200	$ 25,600	2,700
ISO Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period		2 years
ISO Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options vesting period		3 years
ISO Plan [Member] \| Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized \| shares							11,153,872
2001 ISO and NQSO Plan [Member] \| Liability for Class A Redeemable Common Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Financial liabilities			$ 66,500
2012 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options, outstanding \| shares		1,541,165	2,183,127
Exercise price stock options outstanding \| $ / shares		$ 4.12	$ 3.74
Contractual term		10 years
Total requisite service period of awards		4 years
Compensation expense		$ 600	$ 700	$ 600
Compensation cost related to nonvested awards not yet recognized		$ 900
Weighted average period of recognition		2 years 8 months 12 days
2012 Plan [Member] \| Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized \| shares						5,200,000
2017 Plan [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to nonvested awards not yet recognized		$ 5,300
Weighted average period of recognition		4 years
Weighted average grant date fair value of RSUs \| $ / shares		$ 30.96
Number of vesting equal annual installments \| Installment		4
2017 Plan [Member] \| Class A Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance \| shares					8,104,971