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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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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

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

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

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

+ References

No definition available.

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- Definition

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.

+ References

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Share-based Compensation - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 21, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized			$ 6.4
Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized		$ 11.2	$ 11.0
Granted (in shares)		594,536	19,719	656,019
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation expense		$ 21.3	$ 14.3
Weighted average period for compensation expense expected to be recognized		1 year 8 months 12 days	1 year 6 months
RSUs \| Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized		$ 17.9	$ 9.9	$ 6.3
2015 Management Incentive Plan \| Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Expiration period	10 years
Expense recognized		5.8	5.2	$ 5.6
Unrecognized share-based compensation expense		$ 1.6	$ 7.5
Weighted average period for compensation expense expected to be recognized		3 months 19 days	1 year 3 months 18 days
2015 Management Incentive Plan \| RSUs \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years