Share-Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option exercised	300,000	26,000.0
Cash received from stock option exercises	$ 1.5	$ 0.1
Common stock issued pursuant to the vesting of restricted stock units (RSUs)	300,000	300,000
Stock options granted	1,400,000	700,000
Share-based compensation expense	$ 9.0	$ 6.9
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 57.5
Stock vesting period	3 years 1 month 6 days
Stock vesting period	4 years	4 years
Share-based compensation expense	$ 5.7	$ 4.4
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 32.1
Stock vesting period	3 years 1 month 6 days
Stock vesting period	4 years	4 years
Share-based compensation expense	$ 3.3
Restricted stock units granted	400,000	300,000
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 7.5
RSU with performance-based vesting requirements outstanding	400,000
Share-based compensation expense		$ 2.5
Restricted stock units granted		200,000
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

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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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

The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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

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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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