Summary of Significant Accounting Policies - Properties in Development (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Development in Process	$ 192,067,000	$ 224,077,000
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Carrying Costs	(845,868,000)
Other Cost and Expense, Operating	1,500,000	241,000	520,000
Impairment of Real Estate	74,800,000	15,900,000	23,900,000
Impairment Losses Related to Real Estate Partnerships	5,880,000	5,880,000
Deferred Costs, Leasing, Net	55,500,000	56,500,000
Deferred Finance Costs, Net	14,000,000	13,700,000
Properties in Development [Member]
Property, Plant and Equipment [Line Items]
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Carrying Costs	3,500,000	2,100,000
Refundable deposits - development
Property, Plant and Equipment [Line Items]
Real Estate and Accumulated Depreciation, Costs Capitalized Subsequent to Acquisition, Carrying Costs	2,300,000	1,000,000
Construction in Progress
Property, Plant and Equipment [Line Items]
Development in Process	133,153,000	50,903,000
Construction Complete and in Lease-up
Property, Plant and Equipment [Line Items]
Development in Process	0	76,301,000
Land Held for Future Development
Property, Plant and Equipment [Line Items]
Development in Process	58,914,000	96,873,000
Segment, Discontinued Operations [Member]
Property, Plant and Equipment [Line Items]
Impairment of Real Estate	0	3,500,000	6,700,000
Subsidiaries [Member]
Property, Plant and Equipment [Line Items]
Impairment Losses Related to Real Estate Partnerships	$ 0	$ 4,600,000	$ 2,700,000
Minimum [Member] | Construction Complete and in Lease-up
Property, Plant and Equipment [Line Items]
Percentage Of Expected Costs	90.00%
Maximum [Member] | Construction in Progress
Property, Plant and Equipment [Line Items]
Percentage Of Expected Costs	90.00%
Time Period In Which Anchor Has Been Open But Still Considered Construction In Process	2 years
Maximum [Member] | Construction Complete and in Lease-up
Property, Plant and Equipment [Line Items]
Time Period In Which Anchor Has Been Open But Still Considered Construction In Process	2 years