STOCKHOLDERS' DEFICIT - Share-Based Compensation Cost (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Tax benefit related to share-based compensation expense	$ 2.6	$ 4.2	$ 5.0
Unrecognized compensation cost related to arrangements that will vest based on service conditions	$ 17.5
Weighted average period for recognition	3 years
Unrecognized compensation cost related to arrangements that will vest based on market, performance and service conditions	$ 15.1
Corporate expenses
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share-based compensation payments recorded in corporate expenses	$ 10.6	$ 12.1	$ 13.1

Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Rights Market

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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.

+ References

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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

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.

+ References

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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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