Related Parties (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 29, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Related Party Transaction [Line Items]
Net accounts receivable, related parties		$ 1,700,000		$ 1,700,000		$ 2,200,000
Accounts payable and accrued expenses, related parties		6,300,000		6,300,000		8,200,000
Management fees revenue, related parties		1,500,000	1,500,000	4,800,000	4,600,000
Ownership percentage in joint ventures	47.80%	75.00%		75.00%
Proceeds from sale of unconsolidated real estate joint venture, gross	29,100,000
Gain on sale of real estate joint venture and partnership interests	$ 3,500,000	$ 0	$ 0	$ 5,562,000	$ 0