Share Incentive Plans (Details 2) (USD $)	12 Months Ended
Dec. 31, 2010 Year Apartmentunit Hector Property LandParcels Project RealEstate
Information regarding options outstanding and exercisable
Options, Vested and expected to vest	9,718,763
Options, Weighted Average Remaining Contractual Life in Years	5.69
Options, Weighted Average Exercise Price	$ 33.12
Exercise Price Range One [Member]
Information regarding options outstanding and exercisable
Exercise Price Range, Lower Range	$ 21.40
Exercise Price Range, Upper Range	$ 26.75
Options Outstanding, Options	2,974,937
Options Outstanding, Weighted Average Remaining Contractual Life in Years	6.18
Options Outstanding, Weighted Average Exercise Price	$ 23.42
Options Exercisable, Options	1,403,771
Options Exercisable, Weighted Average Exercise Price	$ 23.82
Exercise Price Range Two [Member]
Information regarding options outstanding and exercisable
Exercise Price Range, Lower Range	$ 26.76
Exercise Price Range, Upper Range	$ 32.10
Options Outstanding, Options	2,478,594
Options Outstanding, Weighted Average Remaining Contractual Life in Years	3.09
Options Outstanding, Weighted Average Exercise Price	$ 29.99
Options Exercisable, Options	2,478,594
Options Exercisable, Weighted Average Exercise Price	$ 29.99
Exercise Price Range Three [Member]
Information regarding options outstanding and exercisable
Exercise Price Range, Lower Range	$ 32.11
Exercise Price Range, Upper Range	$ 37.45
Options Outstanding, Options	1,374,888
Options Outstanding, Weighted Average Remaining Contractual Life in Years	9.01
Options Outstanding, Weighted Average Exercise Price	$ 32.96
Options Exercisable, Options	23,546
Options Exercisable, Weighted Average Exercise Price	$ 32.23
Exercise Price Range Four [Member]
Information regarding options outstanding and exercisable
Exercise Price Range, Lower Range	$ 37.46
Exercise Price Range, Upper Range	$ 42.80
Options Outstanding, Options	2,363,450
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5.87
Options Outstanding, Weighted Average Exercise Price	$ 40.44
Options Exercisable, Options	2,023,316
Options Exercisable, Weighted Average Exercise Price	$ 40.75
Exercise Price Range Five [Member]
Information regarding options outstanding and exercisable
Exercise Price Range, Lower Range	$ 42.81
Exercise Price Range, Upper Range	$ 48.15
Options Outstanding, Options	4,202
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5.32
Options Outstanding, Weighted Average Exercise Price	$ 45.25
Options Exercisable, Options	4,202
Options Exercisable, Weighted Average Exercise Price	$ 45.25
Exercise Price Range Six [Member]
Information regarding options outstanding and exercisable
Exercise Price Range, Lower Range	$ 48.16
Exercise Price Range, Upper Range	$ 53.50
Options Outstanding, Options	910,417
Options Outstanding, Weighted Average Remaining Contractual Life in Years	6.09
Options Outstanding, Weighted Average Exercise Price	$ 53.19
Options Exercisable, Options	853,222
Options Exercisable, Weighted Average Exercise Price	$ 53.50
Exercise Price Range Seven [Member]
Information regarding options outstanding and exercisable
Exercise Price Range, Lower Range	$ 21.40
Exercise Price Range, Upper Range	$ 53.50
Options Outstanding, Options	10,106,488
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5.73
Options Outstanding, Weighted Average Exercise Price	$ 33.00
Options Exercisable, Options	6,786,651
Options Exercisable, Weighted Average Exercise Price	$ 34.89

Share Based Compensation hares Authorized Under Stock Option Plans By Exercise Price Range Abstract

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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.

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

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The weighted-average period between the balance-sheet date and expiration date for fully vested and expected to vest options outstanding, which may be expressed in a decimal value for number of years.

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Weighted average exercise price as of the balance sheet date for those share-based payment arrangements exercisable and outstanding.

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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.

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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance-sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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The weighted average price as of the balance-sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

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The weighted-average period remaining as of the balance-sheet date until option expiration pertaining to the outstanding stock options for all option plans in the customized range of exercise prices, which may be expressed in a variety of ways (for example, years, months).

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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.

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