Stock-Based Compensation (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011 years	Dec. 31, 2010 years	Dec. 31, 2009 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of stock options	$ 3.76	$ 9.19	$ 10.87
Weighted-average expected lives of options, years	4.6	7.6	6.9
Total intrinsic value of options exercised	$ 0.2	$ 0.1	$ 2.8
Total share-based compensation expense related to stock options	9.0	12.7	11.3
Stock option expense recognition weighted-average period, years	2
Cash proceeds from the exercise of stock options	9.0	0.1	3.6
Tax benefit realized for stock options			4.3
Unrecognized compensation costs related to stock options	9.8
Non-Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual forfeiture rate	25.00%
Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual forfeiture rate	0.00%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of options exercised	11.8	12.7	13.1
Total share-based compensation expense related to stock options	6.4	4.8	3.8
Stock option expense recognition weighted-average period, years	2
Unrecognized compensation costs related to stock options	$ 14.1

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Weighted Average Expected Lives Of Options

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- Definition

Stock Option Expense Weighted Average 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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- Definition

Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

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As of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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- Definition

Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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- Definition

The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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