Share-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options granted	93,955	73,225
Weighted-average exercise price for stock options granted	$ 33.87	$ 44.06
Weighted-average exercise price for outstanding stock options	$ 33.52
Weighted-average remaining contractual term for outstanding stock options	5.6
Capitalized share-based compensation cost	$ 0	$ 0
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options term (in years)	10
Unrecognized compensation cost	3.0
Weighted-average period for which cost is expected to be recognized, in years	2.2
Service Award Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	1.6
Weighted-average period for which cost is expected to be recognized, in years	1.8
Performance Award Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	2.7
Weighted-average period for which cost is expected to be recognized, in years	3.1
Maximum percentage to return on invested capital for annual performance period	12.00%
Board DSUs And Dividend Equivalents Granted To Board [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation options awarded, vesting period	3 years
Share-based compensation options awarded, number of installments	3
Weighted-average period for which cost is expected to be recognized, in years	1.8
Board DSUs Granted To Nonemployee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation options awarded, vesting period	3 years
Unrecognized compensation cost	1.1
Chief Executive Officer [Member] \| DSU Service Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation options awarded, vesting period	4 years
Chief Executive Officer [Member] \| DSU Performance Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation options awarded, number of installments	4
Unrecognized compensation cost	$ 2.1
Weighted-average period for which cost is expected to be recognized, in years	0.8
Maximum percentage to return on invested capital for annual performance period	12.00%

Maximum percentage to return on invested capital for annual performance period.

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- Definition

Share-based Compensation Arrangement By Share-based Payment Award, Award Vesting, Number Of Installments

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Stock Options Contractual Period

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- Definition

Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

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-Publisher FASB

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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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The weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, using a decimal to express in number of years.

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- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

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- Definition

The weighted average price at which option holders acquired shares when converting their stock options into shares under the plan during the reporting period.

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- Definition

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

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- Definition

The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The weighted average period between the balance sheet date and expiration for all awards outstanding under the plan, which may be expressed in a decimal value for number of years.

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