Related Parties (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Mar. 31, 2010	Sep. 30, 2011	Sep. 30, 2010	Apr. 30, 2011	Dec. 31, 2010
Related Party Transaction [Line Items]
Accounts receivable, related parties	$ 2,400,000			$ 2,400,000			$ 2,700,000
Accounts payable and accrued expenses, related parties	8,000,000			8,000,000			9,600,000
Management fees revenue, related parties	1,500,000	1,400,000		4,600,000	4,300,000
Debt assumed by unconsolidated joint venture			28,100,000
Proceeds from sale and disposition of property, net				52,549,000	17,302,000
Sale of unconsolidated joint venture interest	47.80%			47.80%		50.00%
Anticipated proceeds to be received for an interest in unconsolidated real estate joint ventures	28,800,000
Property Contributed To Joint Venture [Member]
Related Party Transaction [Line Items]
Value of property contributed to unconsolidated joint venture			47,300,000
Debt assumed by unconsolidated joint venture			28,100,000
Proceeds from sale and disposition of property, net			$ 14,000,000