Stock Option And Incentive Plan (Restricted Stock) (Narrative) (Details) (USD $)	3 Months Ended			3 Months Ended		65 Months Ended	3 Months Ended					3 Months Ended
	Mar. 31, 2012 Y	Mar. 31, 2011	Dec. 31, 2011	Mar. 31, 2012 Restricted Stock [Member]	Mar. 31, 2012 LTIP Units [Member] Y	Mar. 31, 2012 LTIPs And Restricted Stock [Member]	Mar. 31, 2012 LTIPs and OPP Awards [Member]	Mar. 31, 2012 OPP Units 2012 [Member]	Mar. 31, 2012 OPP Units 2012 [Member] SNL Equity REIT [Member]	Mar. 31, 2012 Non Qualified Stock Options [Member] Y	Mar. 31, 2012 Unvested 2011 and 2012 OPP Units [Member]	Mar. 31, 2012 Executive Vice President [Member]
Stock Option And Incentive Plan And Stock Purchase Plan [Line Items]
Shares issued	149,463,241		148,186,511	19,521
LTIP units issued					169,301
Non-qualified stock options issued										186,007
2012 OPP units issued								400,000
Employee and director payment per share				$ 0.01			$ 0.25
Vesting annual installments						4
Stock-based compensation associated with restricted stock, LTIP Units, 2008 OPP Units, 2011 OPP Units, and 2012 OPP Units	$ 10,900,000	$ 11,600,000										$ 2,700,000
Accelerated Compensation Expenses Related To 2008 Opp Units		4,300,000
Unrecognized compensation expenses						34,400,000					11,400,000
Weighted-average period (years)	3.0
Value of shares of common stock	1,494,000		1,481,000	2,100,000
Employee's weighted average cost per share				$ 107.57
Value of LTIP units issued					16,800,000
Per unit fair value weighted-average					$ 98.94
Expected life assumed to calculate per unit fair value per LTIP unit (years)					5.8					5.4
Risk-free rate					0.94%			0.35%		0.92%
Expected price volatility					29.10%			31.00%	30.00%	28.40%
Expected dividend rate										2.90%
Value of OPP units								7,700,000
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.		The non-qualified stock options granted during the three months ended March 31, 2012 had a weighted-average fair value on the date of grant of $19.50 per option, which was computed using the Black-Scholes option-pricing model utilizing the following weighted-average assumptions: an expected life of 5.4 years, a risk-free interest rate of 0.92%, an expected price volatility of 28.4% and an expected dividend yield of 2.9%.
Estimated dividend payments, per share								$ 7.28
Weighted-average grant date fair value										$ 19.50
Weighted-average exercise price										$ 107.23