Common Stock Plans (Stock Options, Textual) (Details) (Stock Incentive Plan, USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 5,600,000	$ 4,600,000	$ 4,400,000
Tax benefit related to stock-based compensation	2,100,000	1,700,000	1,600,000
Intrinsic value of stock options exercied during period	4,300,000
Cash received from exercise of stock options	7,500,000
Intrinsic value for outstanding options	10,500,000
Intrinsic value for exercisable options	6,200,000
Fair value of vested options	4,200,000
Unrecognized compensation cost	1,900,000
Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of stock options exercied during period	900,000
Cash paid for settlement of stock apprciation rights	$ 600,000

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Total Fair Value

No definition available.

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- Definition

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.

+ References

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- Definition

Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements.

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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

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

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

The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of vested portions of options outstanding and currently exercisable under the option plan as of the balance sheet date.

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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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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices pertaining to options outstanding under the plan as of the balance sheet date.

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