Equity Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity compensation expense	$ 16.6	$ 11.4
Stock appreciation rights granted	200,000
Stock appreciation rights granted, weighted average exercise price (per share)	$ 150.87
Performance contingent units	100,000
Shares Granted To Non Employee Directors	7,623
Options exercisable (shares)	1,500,000
Options exercisable, weighted average price (per share)	$ 65.70
Options, remaining term	4 years 5 months
Compensation cost not yet recognized	$ 36.9
Period for recognition	1 year 5 months

Performance contingent units issued to employees during the period.

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Number of shares granted to non-employee directors during the period.

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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
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Unrecognized cost of unvested share-based compensation awards.

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-Topic 718
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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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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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