Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financial position of the Real Estate Ventures
Equity Method Investment Summarized Financial Information Debt	$ 724,780
Company's share of equity (Company's basis)	193,555	115,807
Unconsolidated real estate ventures [Member]
Financial position of the Real Estate Ventures
Net property	923,536	846,643
Other Assets	174,677	110,520
Other Liabilities	53,645	48,798
Equity Method Investment Summarized Financial Information Debt	724,780	745,830
Equity	319,788	162,535
Company's share of equity (Company's basis)	$ 193,555	$ 115,807