Investments in and Advances to Other Real Estate Partnerships (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Assets:
Net Investment in Real Estate	$ 2,141,810	$ 2,083,383
Real Estate and Other Assets Held for Sale, Net of Accumulated Depreciation and Amortization of $389 and $4,970	42,930	78,855
Total Assets	2,576,962	2,571,113
Liabilities:
Mortgage Loans Payable	578,851	584,288
Partners' Capital	1,086,280	1,081,992
Total Liabilities and Partners' Capital	2,576,962	2,571,113
Other Real Estate Partnership [Member]
Assets:
Net Investment in Real Estate	262,589	249,984
Real Estate and Other Assets Held for Sale, Net of Accumulated Depreciation and Amortization of $389 and $4,970	1,093	12,804
Note Receivable	145,362	131,908
Other Assets, Net	38,987	41,605
Total Assets	448,031	436,301
Liabilities:
Mortgage Loans Payable	105,127	105,968
Other Liabilities, Net	7,753	8,577
Partners' Capital	335,151	321,756
Total Liabilities and Partners' Capital	$ 448,031	$ 436,301