Impairment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended			9 Months Ended		3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended		9 Months Ended						3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Apr. 30, 2011	Sep. 30, 2010 Sheridan [Member]	Apr. 02, 2010 Sheridan [Member]	Sep. 30, 2011 Land Held For Development And Undeveloped Land [Member]		Sep. 30, 2010 Land Held For Development And Undeveloped Land [Member]		Sep. 30, 2011 Land Held For Development And Undeveloped Land [Member]		Sep. 30, 2010 Land Held For Development And Undeveloped Land [Member]		Sep. 30, 2011 Property Marketed For Sale [Member]		Sep. 30, 2010 Property Marketed For Sale [Member]		Sep. 30, 2011 Property Marketed For Sale [Member]		Sep. 30, 2010 Property Marketed For Sale [Member]		Sep. 30, 2011 Investments In Real Estate Joint Ventures And Partnerships [Member]		Sep. 30, 2011 Investments In Real Estate Joint Ventures And Partnerships [Member]		Sep. 30, 2010 Investments In Real Estate Joint Ventures And Partnerships [Member]		Sep. 30, 2011 Subordinate Tax Increment Revenue Bonds [Member]		Sep. 30, 2011 Property Held For Sale Or Sold [Member]	Sep. 30, 2011 Property Held For Sale Or Sold [Member]	Sep. 30, 2011 Impairment Charges at Equity In Loss Of Real Estate Joint Ventures And Partnerships [Member]	Sep. 30, 2011 Impairment Charges at Equity In Loss Of Real Estate Joint Ventures And Partnerships [Member]	Sep. 30, 2010 Impairment Charges at Equity In Loss Of Real Estate Joint Ventures And Partnerships [Member]	Sep. 30, 2011 Impairment Charges at Net Loss Attributable To Noncontrolling Interests [Member]	Sep. 30, 2011 Impairment Charges at Net Loss Attributable To Noncontrolling Interests [Member]
Impairment losses related to property								$ 23,646	[1]	$ 2,827	[1]	$ 23,646	[1]	$ 2,827	[1]	$ 10,224	[2]	$ 2,114	[2]	$ 11,149	[2]	$ 2,350	[2]									$ 14,845	$ 17,733
Impairment losses related to partially owned real estate joint ventures and partnerships						15,800																		1,474	[3]	1,474	[3]	15,825	[3]
Impairment losses related to tax increment revenue bonds																														18,737	[4]
Total reported in continuing operations	35,344	4,941	55,006	21,002
Total impairment charges	50,189	4,941	72,739	21,002
Equity in loss of real estate joint ventures and partnerships, net	(3,034)	3,455	3,942	9,321																														6,912	7,022	115
Net loss attributable to noncontrolling interests	(2,738)	1,712	(410)	3,093																																	(4,459)	(4,459)
Net impact of impairment charges	$ 52,642	$ 4,941	$ 75,302	$ 21,117
Ownership percentage in joint ventures	47.80%		47.80%		50.00%		50.00%

[1] These impairments were prompted by changes in management's plans for these properties, recent comparable market transactions and a change in market conditions.

[2] These charges resulted from changes in management's plans for these properties, primarily the marketing of these properties for sale.

[3] Amounts reported in 2011 relate to current market conditions and liquidation plans for the underlying individual joint venture properties. 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. See Note 4 for additional information.

[4] During 2011, the tax increment revenue bonds were remarketed by the issuer. 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 (see Notes 15 and 16 for further information).