Debt Of The Operating Partnership (Debt Maturities Table) (Details) (USD $)	3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Debt of the Operating Partnership [Line Items]
Remainder of 2012	$ 79,545,000
2013	247,555,000
2014	483,622,000
2015	1,195,779,000
2016	211,190,000
Thereafter	1,060,766,000
Subtotal	3,278,457,000
Unamortized discounts	(8,681,000)
Unamortized premium	2,072,000
Global revolving credit facility	678,554,000		275,106,000
Unsecured Senior Note	3,278,457,000
Exchangeable senior debentures	266,400,000		266,400,000
Mortgage Loans	875,075,000		947,132,000
Other secured loan	10,500,000		10,500,000
Total indebtedness	3,271,848,000		2,940,210,000
Revolving credit facility commitments extension (years)	1
Global Revolving Credit Facility [Member]
Debt of the Operating Partnership [Line Items]
2015	678,554,000	[1]
Subtotal	678,554,000	[1]
Global revolving credit facility	678,554,000	[1]
Unsecured Senior Note	678,554,000	[1]
Senior Notes	678,554,000	[2]	275,106,000	[2]
Unsecured Senior Notes [Member]
Debt of the Operating Partnership [Line Items]
2013	33,000,000
2015	67,000,000
2016	25,000,000
Thereafter	50,000,000
Subtotal	175,000,000
Unsecured Senior Note	175,000,000
Senior Notes [Member]
Debt of the Operating Partnership [Line Items]
2015	375,000,000
Thereafter	900,000,000
Subtotal	1,275,000,000
Unamortized discounts	(8,681,000)		(8,928,000)
Unsecured Senior Note	1,275,000,000
Senior Notes	1,266,319,000		1,266,072,000
Exchangeable Senior Debentures [Member]
Debt of the Operating Partnership [Line Items]
2014	266,400,000	[3]
Subtotal	266,400,000
Unsecured Senior Note	266,400,000
Exchangeable senior debentures	266,400,000		266,400,000
Mortgage Loans [Member]
Debt of the Operating Partnership [Line Items]
Remainder of 2012	79,545,000	[4]
2013	204,055,000	[4]
2014	217,222,000	[4]
2015	75,225,000	[4]
2016	186,190,000	[4]
Thereafter	110,766,000	[4]
Subtotal	873,003,000	[4]
Unamortized premium	2,072,000	[4]	2,077,000
Unsecured Senior Note	873,003,000	[4]
Mortgage Loans	875,075,000	[4]	947,132,000
Limited recourse guarantees	56,000,000
Partial letter of credit	37,200,000
Other Secured Loans [Member]
Debt of the Operating Partnership [Line Items]
2013	10,500,000
Subtotal	10,500,000
Unsecured Senior Note	10,500,000
Other secured loan	$ 10,500,000		$ 10,500,000

[1] Subject to a one-year extension option exercisable by us. The bank group is obligated to grant the extension option provided we give proper notice, we make certain representations and warranties and no default exists under the global revolving credit facility.

[2] Balances as of March 31, 2012 and December 31, 2011 are as follows (balances, in thousands)

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

[4] 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 March 31, 2012, we had provided limited recourse guarantees with respect to approximately $56.0 million principal amount of the outstanding mortgage indebtedness, and partial letter of credit support with respect to approximately an additional $37.2 million of the outstanding mortgage indebtedness.