Fair Value Measurements (Narrative) (Details) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended				6 Months Ended			12 Months Ended
	Apr. 28, 2011	Mar. 31, 2011	Sep. 30, 2011	Jun. 30, 2011		Jun. 30, 2010	Jun. 30, 2011		Jun. 30, 2010	Dec. 31, 2010
Property, net				$ 3,802,204,000	[1]		$ 3,802,204,000	[1]		$ 3,806,545,000	[1]
Carrying value of bonds										At December 31, 2010, the carrying value of these bonds was equal to its fair value.
Impairment losses related to property				2,600,000		0	3,800,000		300,000
Proceeds from real estate and real estate joint ventures		4,000,000	500,000							8,300,000
Notes receivable from real estate joint ventures and partnerships				159,760,000			159,760,000			184,788,000
Notes receivable from real estate joint ventures and partnerships, fair value				166,100,000			166,100,000			188,000,000
Cash received on exchange of bonds	16,500,000
Impairment loss on investments	18,700,000
Subordinate Tax Increment Revenue Bonds [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Expected future growth rates				1.00%			1.00%
Expected inflation rates				1.00%			1.00%
Subordinate Tax Increment Revenue Bonds [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Expected future growth rates				4.00%			4.00%
Expected inflation rates				2.00%			2.00%
Impaired Property [Member]
Property fair value				6,445,000			6,445,000			2,325,000
Impairment losses related to property							115,000	[2]		2,827,000	[2]
Impaired Property [Member] | Significant Other Observable Inputs (Level 2) [Member]
Property, net				6,200,000			6,200,000
Property fair value				6,445,000			6,445,000
Cost to sell property							300,000
Impaired Property [Member] | Significant Unobservable Inputs (Level 3) [Member]
Property, net										5,100,000
Property fair value										2,325,000
Subordinate Tax Increment Revenue Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Subordinated tax increment revenue bonds at cost										22,400,000
Investment at fair value										10,700,000
Investments				26,700,000			26,700,000
Significant Unobservable Inputs (Level 3) [Member] | Subordinate Tax Increment Revenue Note [Member]
Subordinated tax increment revenue bonds at cost										600,000
Investment at fair value										0
Subordinate Tax Increment Revenue Bonds [Member]
Subordinated tax increment revenue bonds at cost	22,400,000
Impairment loss on investments							18,737,000	[2]		11,717,000	[2]
Agency issued subordinate bonds	57,700,000
Investment at fair value	10,700,000			0			0
Subordinate Tax Increment Revenue Note [Member]
Impairment loss on investments										598,000	[2]
Senior Tax Increment Revenue Bonds [Member]
Investment at fair value	51,300,000
Fixed Rate Debt [Member]
Debt fair value				2,400,000,000			2,400,000,000			2,400,000,000
Variable-Rate Debt [Member]
Debt fair value				$ 341,000,000			$ 341,000,000			$ 252,200,000

[1] Consolidated Variable Interest Entities' Assets and Liabilities included in the above balances (See Note 3):

[2] Total gains (losses) exclude impairments on disposed assets.