Debt Of The Operating Partnership (Debt Maturities Table) (Details) (USD $)			9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 Revolving Credit Facility [Member]		Sep. 30, 2011 Unsecured Senior Notes [Member]	Sep. 30, 2011 Senior Notes [Member]	Dec. 31, 2010 Senior Notes [Member]	Sep. 30, 2011 Exchangeable Senior Debentures [Member]		Dec. 31, 2010 Exchangeable Senior Debentures [Member]	Sep. 30, 2011 Mortgage Loans [Member]		Dec. 31, 2010 Mortgage Loans [Member]	Sep. 30, 2011 Other Secured Loans [Member]	Dec. 31, 2010 Other Secured Loans [Member]
Debt of the Operating Partnership [Line Items]
Remainder of 2011	$ 3,829,000										$ 3,829,000	[1]
2012	321,477,000		163,113,000	[2]							158,364,000	[1]
2013	199,395,000				33,000,000						155,895,000	[1]		10,500,000
2014	482,995,000							266,400,000	[3]		216,595,000	[1]
2015	517,436,000				67,000,000	375,000,000					75,436,000	[1]
Thereafter	1,280,097,000				75,000,000	900,000,000					305,097,000	[1]
Subtotal	2,805,229,000		163,113,000	[2]	175,000,000	1,275,000,000		266,400,000			915,216,000	[1]		10,500,000
Unamortized discounts	(9,172,000)					(9,172,000)	(8,970,000)			(1,456,000)
Unamortized premium	983,000										983,000	[1]	1,101,000
Revolving credit facilities	163,113,000	333,534,000	163,113,000	[2]
Unsecured Senior Note	2,805,229,000		163,113,000	[2]	175,000,000	1,275,000,000		266,400,000			915,216,000	[1]		10,500,000
Senior Notes						1,265,828,000	866,030,000
Exchangeable Senior Debenture	266,400,000	353,702,000						266,400,000		353,702,000
Mortgage Loans	916,199,000	1,043,188,000									916,199,000	[1]	1,043,188,000
Other secured loan	10,500,000	10,500,000												10,500,000	10,500,000
Total indebtedness	2,797,040,000	2,806,954,000
Revolving credit facility commitments extension (years)			1
Limited recourse guarantees											56,500,000
Partial letter of credit											$ 36,500,000

[1] Our mortgage loans are generally non-recourse to us, subject to carve outs for specified actions by us or specified undisclosed environmental liabilities. As of September 30, 2011, we had provided limited recourse guarantees with respect to approximately $56.5 million principal amount of the outstanding mortgage indebtedness, and partial letter of credit support with respect to approximately an additional $36.5 million of the outstanding mortgage indebtedness.

[2] Effective August 31, 2011, we exercised the second and final one-year extension option to our corporate revolving credit facility, which extended its maturity date from August 31, 2011 to August 31, 2012.

[3] Assumes maturity of the 2029 Debentures at first redemption date in April 2014.