Impairment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Asset Impairment [Line Items]
Total reported in continuing operations	$ 6,852		$ 770
Total impairment charges	10,023		1,225
Equity in loss of real estate joint ventures and partnerships, net	4,075		3,397
Net loss attributable to noncontrolling interests	1,441		1,092
Net impact of impairment charges	10,023		1,335
Property Marketed For Sale Or Sold [Member]
Asset Impairment [Line Items]
Impairment losses related to property	244	[1]	770	[1]
Investments In Real Estate Joint Ventures And Partnerships [Member]
Asset Impairment [Line Items]
Impairment losses related to partially owned real estate joint ventures and partnerships	6,608	[2]
Property Held For Sale Or Sold [Member]
Asset Impairment [Line Items]
Impairment losses related to property	3,171	[3]	455	[3]
Impairment Charges At Equity In Loss Of Real Estate Joint Ventures And Partnerships, Net [Member]
Asset Impairment [Line Items]
Equity in loss of real estate joint ventures and partnerships, net			$ 110

[1] These charges resulted from changes in management's plans for these properties, primarily the marketing of these properties for sale. Also included in this caption are impairments associated with dispositions that did not qualify to be reported in discontinued operations.

[2] Amounts reported in 2012 are based on third party offers to buy our interests in industrial real estate joint ventures.

[3] Amounts reported in 2012 are based on third party offers.