Fair Value Measurements (Narrative) (Details) (USD $)	1 Months Ended	6 Months Ended			12 Months Ended		1 Months Ended	12 Months Ended							6 Months Ended		12 Months Ended						6 Months Ended		12 Months Ended					12 Months Ended	6 Months Ended		12 Months Ended						12 Months Ended			12 Months Ended
	Apr. 30, 2011	Jun. 30, 2012		Jun. 30, 2011	Dec. 31, 2011		Apr. 30, 2011 Subordinate Tax Increment Revenue Bonds [Member]	Dec. 31, 2011 Subordinate Tax Increment Revenue Bonds [Member]		Dec. 31, 2010 Subordinate Tax Increment Revenue Bonds [Member]	Apr. 30, 2011 Senior Tax Increment Revenue Bonds [Member]	Jun. 30, 2012 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Subordinate Tax Increment Revenue Bonds [Member]	Jun. 30, 2012 Impaired Property [Member]		Dec. 31, 2011 Impaired Property [Member]		Dec. 31, 2011 Impaired Property [Member] Significant Other Observable Inputs (Level 2) [Member]	Jun. 30, 2012 Impaired Property [Member] Significant Unobservable Inputs (Level 3) [Member]		Dec. 31, 2011 Impaired Property [Member] Significant Unobservable Inputs (Level 3) [Member]	Jun. 30, 2012 Impaired Property Held For Sale [Member]		Dec. 31, 2011 Impaired Property Held For Sale [Member]		Jun. 30, 2012 Impaired Property Held For Sale [Member] Significant Other Observable Inputs (Level 2) [Member]		Dec. 31, 2011 Impaired Property Held For Sale [Member] Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2011 Impaired Property Held For Sale [Member] Significant Unobservable Inputs (Level 3) [Member]	Jun. 30, 2012 Impaired Investment In Real Estate Joint Ventures And Partnerships [Member]		Dec. 31, 2011 Impaired Investment In Real Estate Joint Ventures And Partnerships [Member]		Jun. 30, 2012 Impaired Investment In Real Estate Joint Ventures And Partnerships [Member] Significant Other Observable Inputs (Level 2) [Member]		Dec. 31, 2011 Impaired Investment In Real Estate Joint Ventures And Partnerships [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Minimum [Member] Significant Unobservable Inputs (Level 3) [Member] Subordinate Tax Increment Revenue Bonds [Member]	Dec. 31, 2011 Minimum [Member] Impaired Property [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Minimum [Member] Impaired Investment In Real Estate Joint Ventures And Partnerships [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Maximum [Member] Significant Unobservable Inputs (Level 3) [Member] Subordinate Tax Increment Revenue Bonds [Member]	Dec. 31, 2011 Maximum [Member] Impaired Property [Member] Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Maximum [Member] Impaired Investment In Real Estate Joint Ventures And Partnerships [Member] Significant Unobservable Inputs (Level 3) [Member]
Fair Value Measurements [Line Items]
Property, net		$ 3,409,500,000	[1]		$ 3,702,236,000	[1]									$ 50,700,000		$ 135,500,000
Property fair value															46,375,000	[2]	98,596,000		389,000	46,375,000	[2]	98,207,000
Property held for sale, net		63,747,000			73,241,000																		42,200,000		57,000,000
Property held for sale fair value																							39,131,000	[3]	45,157,000		39,131,000	[3]	43,657,000	1,500,000
Cost to sell property																							800,000		2,000,000
Investment in real estate joint ventures and partnerships, net		317,781,000			341,608,000																										30,800,000		8,100,000
Investment in real estate joint ventures and partnerships fair value																															24,231,000	[4]	6,311,000		24,231,000	[4]	6,311,000
Subordinated bonds received on exchange of bonds							57,700,000
Subordinated tax increment revenue bonds at cost							22,400,000
Investments								26,723,000				26,505,000	26,505,000	26,723,000
Investment at fair value							10,700,000				51,300,000
Cash received on exchange of bonds	16,500,000	0		16,545,000
Impairment losses		$ (14,830,000)	[5]		$ (71,195,000)	[6]		$ (18,737,000)	[6]	$ (11,700,000)					$ (4,293,000)	[2],[5]	$ (36,907,000)	[6]					$ (3,929,000)	[3],[5]	$ (13,799,000)	[6]					$ (6,608,000)	[4],[5]	$ (1,752,000)	[6]
Assumption For Fair Value Discount Rate																														10.00%									8.00%			13.00%
Assumption For Fair Value Market Capitalization Rate																																								7.00%			9.00%
Assumption For Fair Value Expected Future Growth Rate																																						1.00%			4.00%
Assumption For Fair Value Expected Inflation Rate																																						1.00%			2.00%

[1] Consolidated Variable Interest Entities’ Assets and Liabilities included in the above balances (See Note 17):

[2] In accordance with our policy of evaluating and recording impairments on the disposal of long-lived assets, property with a carrying amount of $50.7 million was written down to a fair value of $46.4 million, resulting in a loss of $4.3 million, which was included in earnings for the period. Management’s estimate of the fair value of these properties was determined using Level 3 inputs. See the quantitative information about the significant unobservable inputs used for our Level 3 fair value measurements table below.

[3] Property held for sale with a carrying amount of $42.2 million was written down to a fair value of $39.1 million less costs to sell of $0.8 million, resulting in a loss of $3.9 million, which was included in discontinued operations in the Condensed Consolidated Statements of Operations and Comprehensive Income for the period. Management’s estimate of the fair value of these properties was determined using bona fide purchase offers for the Level 2 inputs.

[4] Our net investment in real estate joint ventures and partnerships with a carrying amount of $30.8 million was written down to a fair value of $24.2 million, resulting in a loss of $6.6 million, which was included in earnings for the period. Management’s estimate of the fair value of this investment was determined using the weighted average of the bona fide purchase offers received for the Level 2 inputs.

[5] Total gains (losses) exclude impairments on disposed assets because they are no longer held by us.

[6] Total gains (losses) are reflected throughout 2011 and exclude impairments on disposed assets because they are no longer held by us.