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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Exercise price per share or per unit of warrants or rights outstanding.

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Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.

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Aggregate number of nonredeemable preferred shares reserved for future issuance.

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Number of shares of preferred stock issued as dividends during the period. Excludes stock splits.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Stockholders' Deficit and Employee Benefit Plans (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Jun. 19, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense		$ 7.5	$ 11.0	$ 20.5	$ 23.5
Series C Junior Participating Stock
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Junior preferred stock reserved for issuance (in shares)	20,000
Preferred stock par value (in dollars per share)	$ 1.00
Number of shares called by each right (in shares)	0.0001
Right purchase price (in dollars per share)	$ 109.00
Preferred shares outstanding (in shares)		0		0
Series A Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Preferred stock par value (in dollars per share)	$ 0.01
Series A Preferred Stock \| Preferred Share Purchase Right
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Preferred share purchase right dividend	1
Preferred shares issued (in shares)		0		0
Related to vesting of stock options
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense		$ 1.1	2.9	$ 2.6	4.2
Related to vesting of RSUs
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense		$ 6.4	$ 8.1	$ 17.9	$ 19.3