Fair Value Measurements (Assets Measured On Nonrecurring Basis) (Details) (USD $)	6 Months Ended		12 Months Ended								12 Months Ended				6 Months Ended		12 Months Ended						6 Months Ended		12 Months Ended						6 Months Ended		12 Months Ended
	Jun. 30, 2012		Dec. 31, 2011		Jun. 30, 2012 Quoted Prices In Active Markets For Identical Assets And Liabilities (Level1) [Member]	Dec. 31, 2011 Quoted Prices In Active Markets For Identical Assets And Liabilities (Level1) [Member]	Jun. 30, 2012 Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2011 Significant Other Observable Inputs (Level 2) [Member]	Jun. 30, 2012 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2011 Subordinate Tax Increment Revenue Bonds [Member]		Dec. 31, 2010 Subordinate Tax Increment Revenue Bonds [Member]	Dec. 31, 2011 Subordinate Tax Increment Revenue Bonds [Member] Significant Unobservable Inputs (Level 3) [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]
Fair Value Measurements [Line Items]
Property															$ 46,375,000	[1]	$ 98,596,000		$ 389,000	$ 46,375,000	[1]	$ 98,207,000
Property held for sale																							39,131,000	[2]	45,157,000		39,131,000	[2]	43,657,000	1,500,000
Investment in real estate joint ventures and partnerships																															24,231,000	[3]	6,311,000		24,231,000	[3]	6,311,000
Investments									26,505,000	26,505,000	26,723,000			26,723,000
Total	109,737,000		176,787,000		0	0	63,362,000	44,046,000	46,375,000	132,741,000
Total Gains (Losses)	(14,830,000)	[4]	(71,195,000)	[5]							(18,737,000)	[5]	(11,700,000)		(4,293,000)	[1],[4]	(36,907,000)	[5]					(3,929,000)	[2],[4]	(13,799,000)	[5]					(6,608,000)	[3],[4]	(1,752,000)	[5]
Property, net	3,409,500,000	[6]	3,702,236,000	[6]											50,700,000		135,500,000
Property held for sale, net	63,747,000		73,241,000																				42,200,000		57,000,000
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

[1] 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.

[2] 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.

[3] 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.

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

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

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