Related Parties (Narrative) (Details) (USD $)	1 Months Ended		12 Months Ended
	Nov. 30, 2012 jvs	Feb. 29, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Apr. 30, 2010
Related Party Transaction [Line Items]
Net accounts receivable, related parties			$ 1,800,000	$ 2,200,000
Accounts payable and accrued expenses, related parties			6,300,000	8,200,000
Management fees revenues, related parties			6,100,000	6,000,000	5,800,000
Ownership percentage in joint ventures		47.80%	75.00%			50.00%
Number of real estate joint ventures	3
Proceeds from sale of unconsolidated joint venture interest, gross	20,900,000	29,100,000
Gain from sale of unconsolidated real estate joint venture interest	$ 8,600,000	$ 3,500,000	$ 14,203,000	$ 0	$ 0
Minimum [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	20.00%
Maximum [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	50.00%
Industrial Properties [Member]
Related Party Transaction [Line Items]
Number of operating properties sold	9		54	3