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

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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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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Unrecognized cost of unvested options awarded to employees as compensation.

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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 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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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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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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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Number of executive officer.

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Share based compensation arrangement by share based payment award equity instruments other than options expected to vest number.

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Stock-Based Compensation - Additional Information (Detail)	1 Months Ended		3 Months Ended		9 Months Ended
	Jul. 30, 2018 Officer	Nov. 30, 2017 Officer	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value of options granted, per share \| $ / shares					$ 5.02	$ 3.18
Grant date fair value of options vested					$ 4,300,000	$ 2,900,000
Aggregate intrinsic value of option exercised					11,600,000	1,800,000
Unrecognized compensation cost			$ 28,900,000		$ 28,900,000
Weighted average period for recognition of compensation costs					3 years 3 months 18 days
RSUs Granted \| shares					1,767,542
Stock based compensation expenses			7,179,000	$ 984,000	$ 10,052,000	2,766,000
Stock-based compensation expense capitalized			0	$ 0	0	0
Stock-based compensation					$ 10,052,000	$ 2,766,000
Separation and Consulting Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation			$ 3,700,000
Separation and Consulting Agreement \| Maximum \| Key Executive One Individual
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			12 months
Separation and Consulting Agreement \| Maximum \| Key Executive Two Individuals
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			6 months
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average period for recognition of compensation costs					2 years 9 months 18 days
Number of executive officer \| Officer	2	1
Vesting period	3 years
RSUs Granted \| shares					1,800,000	0
Stock based compensation expenses					$ 1,200,000	$ 0
Unrecognized stock based compensation cost			$ 14,600,000		$ 14,600,000
Shares expected to vest \| shares			1,627,261		1,627,261