Share-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-recurring share-based compensation charge, recorded	$ 7,700
Stock option exercised	700,000	300,000
Cash received from stock option exercises	$ 16,100	$ 1,500
Common stock issued pursuant to the vesting of restricted stock units (RSUs)	400,000	300,000
Stock options granted	800,000	1,400,000
Share-based compensation expense	$ 19,879	$ 8,976
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 67,700
Stock vesting period	3 years 2 months 12 days
Stock vesting period	4 years	4 years
Share-based compensation expense	$ 13,600	$ 5,700
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 62,000
Stock vesting period	3 years 3 months 18 days
Stock vesting period	4 years	4 years
Share-based compensation expense	$ 6,300	$ 3,300
Restricted stock units granted	500,000	400,000
Performance-based RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost	$ 21,500
RSU with performance-based vesting requirements outstanding	400,000
Restricted stock units granted	200,000	0
Performance-based RSUs \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	4 years
Performance-based RSUs \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock vesting period	5 years

Non recurring share based compensation expense.

No definition available.

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- Definition

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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- Definition

Unrecognized cost of unvested share-based compensation awards.

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- Definition

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

Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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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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- Definition

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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- Definition

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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No definition available.

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

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- Definition

Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards.

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

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