Impairment (Schedule Of Impairment Charges) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Feb. 29, 2012	Apr. 30, 2010
Asset Impairment [Line Items]
Total reported in continuing operations					$ 9,982		$ 55,574		$ 33,317
Total impairment charges					15,436		75,874		33,317
Equity in loss of real estate joint ventures and partnerships, net					(1,558)		7,834		12,889
Net loss attributable to noncontrolling interests					5,781		1,118		5,032
Net impact of impairment charges	24,900	10,000	52,600	21,300	35,382		78,437		33,432
Ownership percentage in joint ventures					75.00%						47.80%	50.00%
Sheridan [Member]
Asset Impairment [Line Items]
Ownership percentage in joint ventures									50.00%
Tax Increment Revenue Bonds And Notes [Member]
Asset Impairment [Line Items]
Impairment losses related to tax increment revenue bonds					0	[1]	18,737	[1]	12,315	[1]
Land Held For Development And Undeveloped Land [Member]
Asset Impairment [Line Items]
Impairment losses related to property					0	[2]	23,646	[2]	2,827	[2]
Property Marketed For Sale Or Sold [Member]
Asset Impairment [Line Items]
Impairment losses related to property					3,374	[3]	11,439	[3]	2,350	[3]
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	[4]	1,752	[4]	15,825	[4]
Property Held For Sale Or Sold [Member]
Asset Impairment [Line Items]
Impairment losses related to property					5,454		20,300		0
Impairment Charges At Equity In Loss Of Real Estate Joint Ventures And Partnerships [Member]
Asset Impairment [Line Items]
Equity in loss of real estate joint ventures and partnerships, net					19,946		7,022		115
Impairment Charges At Net Loss Attributable To Noncontrolling Interests [Member]
Asset Impairment [Line Items]
Net loss attributable to noncontrolling interests					$ 0		$ (4,459)		$ 0

[1] During 2011, the tax increment revenue bonds were remarketed by the Agency. All of the outstanding bonds were recalled, and new bonds were issued. We recorded an $18.7 million net credit loss on the exchange of bonds associated with our investment in the subordinated tax increment revenue bonds. In 2010, we wrote down the value of our subordinated tax increment revenue bonds and notes due to change in holding status of the bonds.

[2] Impairment was prompted by changes in management's plans for these properties, recent comparable market transactions and/or a change in market conditions.

[3] 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.

[4] Amounts reported in 2012 were based on third party offers to buy our interests in industrial real estate joint ventures. Amounts reported in 2011 relate to market conditions. The amount reported in 2010 represents an impairment loss recognized in connection with the revaluation of our 50% equity interest in a development project in Sheridan, Colorado, as a result of our assumption of control of the project as of April 1, 2010.