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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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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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 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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Number of additional shares authorized for issuance under an established share-based compensation plan.

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

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The number of shares purchased on the open market during the period for issuance to employees under the plan.

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Intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options.

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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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Equity Plans and Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended	9 Months Ended
	May 28, 2014	May 31, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding stock awards granted			5,683,000	5,683,000		3,555,000
Stock-based compensation expense				$ 17,135	$ 10,844
Increase in aggregate number of shares of common stock authorized for issuance		600,000
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate intrinsic value			$ 22,300	$ 22,300
Restricted stock unit awards outstanding			1,795,000	1,795,000		2,443,000
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding stock awards granted			151,000	151,000
Employee Stock Option \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				3 years
Expiration period				7 years
Employee Stock Option \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Expiration period				10 years
Performance Based Vesting Condition
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock unit awards outstanding			12,500	12,500
Stock-based compensation expense			$ 400	$ 1,100
Performance Based Vesting Condition Not Probable
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock unit awards outstanding			12,500	12,500
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Newly reserved shares of common stock		5,000,000
Shares remaining available for future purchases		140,250
Outstanding stock awards granted		7,477,619
Time Based Vesting Schedule
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost related to non-vested equity awards			$ 31,200	$ 31,200
Total unrecognized compensation cost, weighted-average vesting period				2 years
Performance Based Vesting Schedule
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total unrecognized compensation cost related to non-vested equity awards			$ 700	$ 700
2014 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares remaining available for future purchases			573,034	573,034
Shares issued to employees				125,193
2014 Employee Stock Purchase Plan \| The commencement of the offer period (generally, the sixteenth day in February or August)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price per share as percentage of fair market value of common stock	85.00%
2014 Employee Stock Purchase Plan \| The exercise date, which is the last day of a purchase period (generally, the fifteenth day in February or August)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price per share as percentage of fair market value of common stock	85.00%