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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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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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 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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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued 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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The number of shares newly issued during the reporting period under the plan.

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For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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Stock-Based Compensation (Details) (USD $) In Millions, except Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	$ 2.9	$ 2.8	$ 10.0	$ 7.2
Income tax benefit from compensation expense	1.1	1.1	3.9	2.8
Stock-Based Compensation Activity
Shares Issued in Period	14,718		284,423
Shares Paid for Tax Withholding for Share Based Compensation	1,150		3,810
Cash Received from Exercise of Stock Options			0.8
Tax Benefit Realized from Exercise of Stock Options	0		0
Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	2.7	2.5	9.3	6.5
Total Shareholder Return [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	1.9	1.5	5.6	4.7
Performance Units Related to Earnings Per Share [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	0.8	1.0	3.7	1.8
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation Expense	0.2	0.3	0.7	0.7
Stock-Based Compensation Activity
Restricted Stock Granted - Number of Shares	14,218
Restricted Stock Granted - Fair Value	$ 49.24
Maximum [Member]
Stock-Based Compensation Activity
Cash Received from Exercise of Stock Options	$ 0.1