Related Parties (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 property	Dec. 31, 2012	Dec. 31, 2011	Dec. 23, 2013
Related Party Transaction [Line Items]
Net accounts receivable, related parties	$ 1,400,000	$ 1,800,000
Accounts payable and accrued expenses, related parties	5,600,000	6,300,000
Management fees revenues, related parties	5,000,000	6,100,000	6,000,000
Ownership percentage in joint ventures	50.00%	75.00%		50.00%
Number of operating properties sold	20
Gain from sale of real estate joint venture and partnership interests	33,670,000	14,203,000	0
Tenancy In Common [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	10.00%	79.60%
Number of real estate joint ventures	2
Gross proceeds, related parties	8,900,000
Consoldiated Real Estate Joint Ventures [Member]
Related Party Transaction [Line Items]
Number of real estate joint ventures	2
Unconsolidated Real Estate Joint Ventures [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	51.00%	47.80%
Number of real estate joint ventures	2
Number of operating properties sold	5
Gain from sale of real estate joint venture and partnership interests	1,900,000
Unconsolidated Real Estate Joint Ventures [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	20.00%	10.00%
Unconsolidated Real Estate Joint Ventures [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures	75.00%	75.00%
Industrial Properties [Member]
Related Party Transaction [Line Items]
Number of real estate joint ventures		3
Gross proceeds, related parties		20,900,000
Gain from sale of real estate joint venture and partnership interests		8,600,000
Industrial Properties [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures		20.00%
Industrial Properties [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures		50.00%
Industrial Properties [Member] | Industrial Properties [Member]
Related Party Transaction [Line Items]
Number of operating properties sold		9
47.8% Joint Venture Interest [Member]
Related Party Transaction [Line Items]
Ownership percentage in joint ventures		47.80%
Gross proceeds, related parties		29,100,000
Gain from sale of real estate joint venture and partnership interests		$ 3,500,000