Stock Option and Incentive Plan (Restricted Stock and LTIP Units) (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended		48 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2009	Dec. 31, 2010
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Shares issued	147,706,147		147,706,147			140,278,005
Non-qualified stock options issued			146,844
LTIP units issued	190,067		190,067
2011 OPP units issued			400,000
Value of shares of common stock	$ 1,476,000		$ 1,476,000			$ 1,402,000
Stock-based compensation associated with restricted stock, LTIP Units, and 2011 OPP Units	5,600,000	6,100,000	22,700,000	26,000,000
Accelerated amount of unvested compensation expense					5,800,000
Accelerated compensation expenses related to 2008 OPP units			4,300,000
Restricted Stock [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Shares issued	19,030		19,030
Employee and director payment per share			$ 0.01
Value of shares of common stock	1,800,000		1,800,000
Employee's cost per share	$ 93.40		$ 93.40
LTIP Units [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Expected price volatility			30.00%
Risk-free rate			2.22%
Expected life assumed to calculate per unit fair value per LTIP unit (years)			5.8
Value of LTIP units issued			16,500,000
Per unit fair value weighted-average	$ 86.74		$ 86.74
LTIPs And Restricted Stock [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Vesting annual installments			4
Unrecognized compensation expenses	29,500,000		29,500,000
OPP Units Two Thousand And Eleven [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Aggregate value of 2011 OPP Awards			7,800,000
Expected price volatility			41.00%
Risk-free rate			0.98%
Estimated dividend payments			6.10
Unrecognized compensation expenses	$ 6,100,000		$ 6,100,000
Weighted-average period (years)			2.6
TRS measurement, years			3
Method of valuation			The Monte Carlo simulation used a statistical formula underlying the Black-Scholes and binomial formulas and such simulation was run approximately 100,000 times.
OPP Units Two Thousand And Eleven [Member] | SNL Equity REIT Index [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Expected price volatility			37.00%
OPP Units Two Thousand And Eight [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
TRS measurement, years			3
Non-Qualified Stock Options [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Expected price volatility			35.00%
Risk-free rate			2.37%
Fair value per option on grant date			$ 24.67
Expected life assumed to calculate per unit fair value per LTIP unit (years)			6.0
Dividend yield			3.00%
Exercise price on option grant date	$ 92.71		$ 92.71
LTIP And OPP Awards [Member]
Stock Option And Incentive Plan And Stock Repurchase Plan [Line Items]
Employee and director payment per share			$ 0.25