Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in valuation, interest rate swaps	$ (2,600,000)		$ (7,700,000)
Goodwill, Impairment Loss		1,500,000		1,700,000
Impairment loss on income producing properties sold or held for sale		36,714,000	3,425,000	37,991,000
Impairment of Real Estate		18,200,000		18,200,000
Discontinued Operation, Provision for Loss (Gain) on Disposal, Less Portion Attributable to Goodwill, Net of Tax, Total		(35,500,000)		(36,800,000)
Term Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term loan notional amount	250,000,000		250,000,000
Term Loan And Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Fair Value, Gross Liability	7,700,000		7,700,000
Definition of Assets Held for Sale Not Met [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Real Estate				6,400,000
Development Intentions Changed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of Real Estate		$ 11,800,000	$ 11,800,000