Investment in Unconsolidated Ventures (Summary of Results of Operations of Unconsolidated Real Estate Ventures) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Summary of results of operations of Real Estate Ventures
Company's share of income (Company's basis)	$ 3,775,000		$ 5,305,000		$ 4,069,000
Unconsolidated real estate ventures [Member]
Summary of results of operations of Real Estate Ventures
Revenue	145,867,000	[1]	118,923,000	[1]	105,236,000
Operating expenses	63,715,000	[1]	44,942,000	[1]	38,691,000
Interest expense, net	42,032,000	[1]	37,505,000	[1]	30,858,000
Depreciation and amortization	39,172,000	[1]	32,703,000	[1]	36,700,000
Net income	948,000	[1]	3,773,000	[1]	(1,012,000)
Company's share of income (Company's basis)	3,775,000	[1]	5,305,000	[1]	4,069,000
Guaranteed repayment of loans on behalf of a certain Real Estate Venture	$ 700,000

[1] Includes the three real estate ventures that were deconsolidated upon the adoption of the accounting standard for the consolidation of VIEs on January 1, 2010.