Share Incentive Plans (Details 1) (USD $)	12 Months Ended
Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2010
Award activity of the Share Incentive Plans
Common Shares Subject to Options, Beginning Balance	11,349,750	9,473,259	9,185,141
Common Shares Subject to Options, Awards granted	1,436,115	2,541,005	1,436,574
Common Shares Subject to Options, Awards exercised/vested	(2,506,645)	(422,713)	(995,129)
Common Shares Subject to Options, Awards forfeited	(76,275)	(146,151)	(113,786)
Common Shares Subject to Options, Awards expired	(96,457)	(95,650)	(39,541)
Common Shares Subject to Options, Ending Balance	10,106,488	11,349,750	9,473,259
Weighted Average Exercise Price per option, Beginning Balance	$ 32.03	$ 33.94	$ 32.37
Weighted Average Exercise Price per option, Awards granted	$ 33.59	$ 23.08	$ 38.46
Weighted Average Exercise Price per option, Awards exercised/vested	$ 28.68	$ 21.62	$ 24.75
Weighted Average Exercise Price per option, Awards forfeited	$ 29.43	$ 30.07	$ 43.95
Weighted Average Exercise Price per option, Awards expired	$ 42.69	$ 32.21	$ 35.91
Weighted Average Exercise Price per option, Ending Balance	$ 33.00	$ 32.03	$ 33.94
Restricted Shares, Beginning Balance	954,366	996,011	1,178,188
Restricted Shares, Awards granted	270,805	362,997	524,983
Restricted Shares, Awards exercised/vested	(278,183)	(340,362)	(644,131)
Restricted Shares, Awards forfeited	(35,038)	(64,280)	(63,029)
Restricted Shares, Ending Balance	911,950	954,366	996,011
Weighted Average Fair Value per Restricted Share, Beginning Balance	$ 37.10	$ 44.16	$ 42.30
Weighted Average Fair Value per Restricted Share, Awards granted	$ 34.85	$ 22.62	$ 38.29
Weighted Average Fair Value per Restricted Share, Awards exercised/vested	$ 52.25	$ 42.67	$ 35.99
Weighted Average Fair Value per Restricted Share, Awards forfeited	$ 30.84	$ 35.28	$ 44.87
Weighted Average Fair Value per Restricted Share, Ending Balance	$ 32.05	$ 37.10	$ 44.16
LTIP Unit, Awards granted	94,096	155,189
Weighted Average Fair Value per LTIP Unit, Awards granted	$ 32.97	$ 21.11
LTIP Unit, Awards forfeited	(1,204)	(573)
Weighted Average Fair Value per LTIP Unit, Beginning Balance	$ 21.11			$ 25.62
Weighted Average Fair Value per LTIP Unit, Awards forfeited	$ 21.11	$ 21.11
LTIP Unit, Ending Balance	247,508	154,616
LTIP Unit, Beginning Balance	247,508	154,616

Award activity of the Share Incentive Plans

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The number of units under a long-term incentive plan that were settled during the reporting period due to a failure to satisfy vesting conditions.

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The weighted average fair value as of the grant date of long term incentive plans that were not exercised during the reporting period as a result of occurrence of a terminating event specified in the contractual agreement.

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The number of long-term incentive plan units issuable under a long-term incentive plan pertaining to grants made during the period.

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The weighted average par value at grant for nonvested long-term incentive plan units issued during the period.

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The number of outstanding units at the balance sheet date for which the employee is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to the proceeds.

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The weighted average fair value of nonvested long-term incentive plan units at the balance sheet date for which the employee is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria to gain title.

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The number of shares under a share-based award plan other than a stock option plan that were settled during the reporting period due to a failure to satisfy vesting conditions pertaining to all option plans.

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The weighted average fair value as of the grant date of share-based award plans other than stock option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

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The number of shares issuable under a share-based award plan pertaining to grants made during the period on other than stock option plans (for example, phantom stock plan, stock appreciation rights plan, performance target plan).

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The weighted average fair value at grant for nonvested share-based awards issued during the period on other than stock option plans (for example, phantom stock plan, stock appreciation rights plan, performance target plan).

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The number of outstanding awards on nonstock option plans (for example, phantom stock plan, stock appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares.

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The weighted average fair value of nonvested awards on share-based plans excluding option plans (for example, phantom stock plan, stock appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares.

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The decrease in the number of shares potentially issuable under a share-based award plan pertaining to awards for which the grantee has gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares, other instruments, or cash in accordance with the terms of the arrangement.

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The weighted average fair value as of grant dates pertaining to a share-based award plan other than a stock option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares, other instruments, or cash in accordance with the terms of the arrangement.

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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.

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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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The decrease in the number of shares that could be issued attributable to the lapse of rights to exercise previously issued stock options under the terms of the option agreements under the plan during the reporting period.

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The weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that lapsed during the reporting period.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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The weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated during the reporting period due to noncompliance with plan terms during the reporting period.

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The quantity of shares issuable on stock options awarded under the plan during the reporting period.

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The weighted average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on stock options awarded under the plan during the reporting period.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance-sheet date, including vested options.

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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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