Share Based Compensation (Narrative) (Details) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Units available under the 2011 Share Plan	5,800,000		5,800,000
Options exercised			327,454	100,000
Exercised price minimum			$ 30.06
Exercised price maximum			$ 48.02
Total intrinsic value of options exercised			$ 5,000,000	$ 1,300,000
Total unrecognized compensation cost related to unvested options which is expected to be amortized	1,800,000		1,800,000
Expected amortized period of unrecognized compensation expected to be recognized for share-based compensation plans			3
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term			3.5
Remaining contractual life (years) outstanding options			4.7
Remaining contractual life (years) exercisable options			3.5
Unamortized value of unvested share awards	34,000,000		34,000,000
Expected Period of amortization of unamortized value of unvested share awards			5
Fair value of shares vested			11,000,000	10,100,000
Vested share awards outstanding	2,600,000		2,600,000
Vested share weighted average issuance price	$ 39.43		$ 39.43
Total compensation cost for option and share awards	3,200,000	2,900,000	6,200,000	6,200,000
Total capitalized compensation cost for option and share awards	$ 300,000	$ 200,000	$ 600,000	$ 500,000.0
2011 Share Incentive Plan [Member]
Fungible units to be issued	9,100,000		9,100,000
Fungible units-to-full value award conversion ratio			83.00
2002 Share Incentive Plan [Member]
Common shares which could be granted pursuant to full value awards	2,700,000		2,700,000
Units available under the superceded 2002 Share Plan	3,300,000		3,300,000
Fungible units-to-full value award conversion ratio			345.00

Common shares which could be granted pursuant to full value awards based on the 3.45 to 1.0 fungible unit-to-full value award conversion ratio.

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Fungible Units To Full Value Award Conversion Ratio

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Shares reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable, specifically for the 2011 Share Plan, which superceded the 2002 Share Plan.

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Shares reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable, specifically from the 2002 Share Plan, which has been superceded by the 2011 Share Plan.

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Options Vested In Period Total Fair Value.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph g(1)

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph h

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- Definition

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

+ References

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-Name Statement of Financial Accounting Standard (FAS)
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As of the latest balance-sheet date presented, the total compensation cost related to outstanding, nonvested share-based compensation awards not yet recognized (will be charged against earnings as services are performed or other vesting criteria are met).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
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The weighted average period over which unrecognized share-based compensation costs are expected to be reported.

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- Definition

Share-based compensation cost during the period with respect to the award, which will be recognized in income (as well as the total recognized tax benefit) or capitalized as part of the cost of an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph g(1)

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Statement of Financial Accounting Standard (FAS)
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- Definition

The difference between the maximum number of shares authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares already issued upon exercise of options or other share-based awards under the plan, and 2) shares reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

The weighted average period between the balance-sheet date and expiration for all vested portions of options outstanding and currently exercisable (or convertible) under the plan, which may be expressed in a decimal value for number of years.

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- Definition

The decrease in the number of reserved shares that could potentially be issued attributable to the exercise or conversion during the reporting period of previously issued stock options under the option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph b(1)(e)

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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.

+ References

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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph a

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- Definition

As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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-Subparagraph d(1)

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- Definition

As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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- Definition

The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

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-Number 123R
-Paragraph 64

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