Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Financial position of the Real Estate Ventures
Company's share of equity (Company's basis)	$ 127,536	$ 115,807
Unconsolidated real estate ventures [Member]
Financial position of the Real Estate Ventures
Net property	845,705	846,643
Other Assets	131,347	110,520
Other Liabilities	51,005	48,798
Debt	682,558	745,830
Equity	243,489	162,535
Company's share of equity (Company's basis)	$ 127,536	$ 115,807