Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
Dec. 31, 2010 Year Apartmentunit Hector Property LandParcels Project RealEstate	Dec. 31, 2009 Apartmentunit LandParcels Year Property Hector Project	Dec. 31, 2008 Property Apartmentunit Hector Year
Weighted average assumptions used to estimate the fair value for the Company's share options
Expected volatility	32.40%	26.80%	20.30%
Expected life	5	5	5
Expected dividend yield	4.85%	4.68%	4.95%
Risk-free interest rate	2.29%	1.89%	2.67%
Option valuation per share	$ 6.18	$ 3.38	$ 4.08
Short-term Debt [Line Items]
Unsecured Notes, face amount	650,000,000
Convertible Notes, stated interest rate		5.60%
Convertible Notes Payable [Member]
Short-term Debt [Line Items]
Unsecured Notes, face amount	650,000,000
Convertible Notes, issuance date	Aug-2006
Convertible Notes, maturity date	Aug. 15, 2026
Effective interest rate for conversion option	5.80%
Interest expense recognized in relation to nonconvertible debt	$ 18,600,000	$ 20,600,000	$ 24,400,000
Convertible Notes, stated interest rate	3.85%	3.85%	3.85%

The effective interest rate on the liability component of convertible debt instrument which may be settled in cash upon conversion, including partial cash settlement.

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Interest expense related to convertible debt instruments which has been recognized for the period, including the contractual interest coupon and amortization of the debt discount, if any.

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The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

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Interest rate stated in the contractual debt agreement.

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-Publisher SEC

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Date when the debt instrument was issued, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

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Date when the debt instrument is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The period of time a share-based award is expected to be outstanding. A share-based award's expected term shall be determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior. An entity is required to aggregate individual awards into relatively homogeneous groups.

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The estimated measure of the percentage amount by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Disclosure of the weighted average expected dividend for an entity using a valuation technique with different dividend rates during the contractual term.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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