Share-Based Compensation Plans (Textuals) (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Share-based compensation	$ 9.0	$ 9.0
Shares Awarded (in shares)	330
Stock-Based Compensation Plans (Textual) [Abstract]
Proceeds from exercise of employee stock options	$ 4.0	$ 3.0
Total intrinsic value of options exercised	4.1
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Unamortized compensation expense	$ 10.0
Weighted average period	2 years 3 months 18 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award
Unamortized compensation expense	$ 32.0
Weighted average period	2 years 3 months 18 days
Shares Awarded (in shares)	230
Performance Based Shares
Share-based Compensation Arrangement by Share-based Payment Award
Unamortized compensation expense	$ 25.0
Weighted average period	2 years 2 months 12 days

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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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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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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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.

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

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Stock-based compensation plans.

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