Stock Option And Incentive Plan (Restricted Stock) (Narrative) (Detail) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended	1 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Executive Vice President [Member]	Jan. 25, 2012 OPP Units 2012 [Member] Y	Sep. 30, 2012 OPP Units 2012 [Member]	Sep. 30, 2012 OPP Units 2012 [Member] SNL Equity REIT [Member]	Sep. 30, 2012 Restricted Stock [Member]	Sep. 30, 2012 Non Qualified Stock Options [Member]	Sep. 30, 2012 LTIP Units [Member]	Sep. 30, 2012 LTIPs And OPP Awards [Member]	Sep. 30, 2012 LTIPs And Restricted Stock [Member] Installment	Sep. 30, 2012 Unvested 2011 And 2012 OPP Units [Member]	Sep. 30, 2012 OPP Units 2008 [Member] Y
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 nine months ended September 30, 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%.	The LTIP Units granted during the nine months ended September 30, 2012 were valued at approximately $17.3 million ($98.83 per unit fair value weighted-average) using a Monte Carlo simulation method model. The weighted-average per unit fair value of each LTIP Unit granted was estimated on the date of grant using the following assumptions: an expected life of 5.8 years, a risk-free interest rate of 0.94% and an expected price volatility of 29.1%.
Expected price volatility								31.00%	30.00%		28.40%	29.10%
Risk-free rate								0.35%			0.92%	0.94%
Estimated dividend payments, per share								7.28
Shares issued	150,935,137		150,935,137		148,186,511					20,756
Non-qualified stock options issued											186,007
LTIP Units issued												174,650
2012 OPP Units issued								400,000
Employee and director payment per share										$ 0.01			$ 0.25
Vesting annual installments														4
Value of shares of common stock	1,509,000		1,509,000		1,481,000					2,200,000
Weighted-average grant date fair value											$ 19.50
Expected life assumed to calculate per unit fair value per LTIP unit (years)											5 years 4 months 24 days	5 years 9 months 18 days
Expected dividend rate											2.90%
Employee's weighted average cost per share										$ 107.31
Weighted-average exercise price											$ 107.23
Value of LTIP Units issued												17,300,000
Per unit fair value weighted-average												$ 98.83
Stock-based compensation expense associated with restricted stock non-qualified stock options, LTIP Units, 2008 OPP Units, 2011 OPP Units and 2012 OPP Units	6,400,000	5,600,000	23,800,000	22,700,000		2,700,000
TRS measurement, years							3									3
Accelerated Compensation Expenses Related To 2008 Opp Units				4,300,000
Unrecognized compensation expenses														$ 24,400,000	$ 9,400,000
Weighted-average period (years)															2 years 8 months 12 days