Investment in Partially Owned Entities (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Equity Method Investments [Line Items]
Depreciation	$ 342	$ 5	$ 84
Liabilities and Equity
Carrying value of investments in unconsolidated entities	253,799	316,711
Net excess of cost of investments over net book value of underlying net assets, Accumulated depreciation	1,714	1,372
Statements of Operations:
Revenues	202,155	283,913	287,694
Interest Income (Expense), after Provision for Loan Loss	63,233	91,965	90,857
Expenses:
Depreciation and amortization	83,324	111,699	99,254
Operating expenses, ground rent and general and administrative expenses	(76,149)	(159,539)	(100,954)
Impairment	(553)	(21,017)	(14,019)
Total expenses	223,259	384,220	305,084
Net loss before gain on sale of real estate	(21,104)	(100,319)	(17,390)
Gain on sale of real estate	9,484	9,219	553
Net income	(11,620)	(91,100)	(16,837)
Company's share of:
Net loss, net of excess basis depreciation of $342, $5 and $84	1,998	(12,802)	(18,684)
Unconsolidated Entities [Member]
Assets:
Real estate assets, net of accumulated depreciation	1,437,268	1,949,035
Equity Methoid Investment, Summarized Financial Information, Other Liabilities	222,096	485,887
Total Assets	1,659,364	2,434,922
Liabilities and Equity
Mortgage debt	1,062,086	1,402,462
Other liabilities	89,573	94,361
Equity	507,705	938,099
Total Liabilities and Equity	1,659,364	2,434,922
Company's share of equity	252,994	307,684
Net excess of cost of investments over net book value of underlying net assets (net of accumulated depreciation of $1,714 and $1,372, respectively)	805	9,027
Carrying value of investments in unconsolidated entities	253,799	316,711
Expenses:
Impairment	$ (9,365)	$ (113,621)	$ (11,239)