Share-based compensation arrangement by share-based payment award number of installments.

No definition available.

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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

Unrecognized cost of unvested options awarded to employees as compensation.

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- Definition

Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

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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 weighted average fair value at grant date for nonvested equity-based awards issued 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

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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- Definition

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.

+ References

No definition available.

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- Definition

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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- Definition

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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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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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

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

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

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-SubTopic 10
-Section 50
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Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Millions			3 Months Ended	6 Months Ended
	Oct. 06, 2017 USD ($) shares	Jan. 04, 2016 shares	Dec. 31, 2017 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) Installment $ / shares shares	Jun. 30, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options exercised \| shares				135,000
Aggregate intrinsic value of stock options exercised				$ 1.8
Options to purchase common stock, outstanding \| shares			3,800,000	4,534,000	3,876,000
Weighted average remaining contractual term				8 years	8 years 3 months 18 days
Weighted average exercise price \| $ / shares			$ 17.75	$ 19.13	$ 17.60
Weighted average grant date fair value of options granted \| $ / shares				$ 15.35	$ 14.14
Unrecognized stock-based compensation expense				$ 32.8
Unrecognized compensation costs, weighted-average recognition periods				2 years 9 months 18 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, number of shares granted \| shares	122,800	189,300		239,366
Grant date fair value of restricted common stock units under performance-based vesting	$ 2.2		$ 1.6
Unrecognized stock-based compensation expense				$ 5.1
Unrecognized compensation costs, weighted-average recognition periods				3 years 4 months 24 days
Weighted average grant date fair value, shares granted, per share \| $ / shares				$ 22.90
Share based compensation, award vesting rights				The RSUs vest in four substantially equal installments on each of the first four anniversaries of the vesting commencement date, subject to the employee's continued employment with, or services to, the Company on each vesting date.
Restricted Stock Units (RSUs) [Member] \| First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments \| Installment				4
Restricted Stock Units (RSUs) [Member] \| Second Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments \| Installment				4
Restricted Stock Units (RSUs) [Member] \| Third Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments \| Installment				4
Restricted Stock Units (RSUs) [Member] \| Fourth Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments \| Installment				4
Restricted Stock Units (RSUs) [Member] \| January 4, 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense				$ 0.6
Unrecognized compensation costs, weighted-average recognition periods				2 years