Commitments and Contingencies (Details) (USD $)	6 Months Ended					6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 NBCR Losses [Member]	Jun. 30, 2012 Earthquake California Properties [Member]	Jun. 30, 2012 All Risk And Rental Value [Member]	Jun. 30, 2012 General Liability [Member]	Jun. 30, 2012 PPIC [Member] NBCR Losses [Member]	Jun. 30, 2012 Stop & Shop [Member]	Jan. 12, 2012 Stop & Shop [Member]	Dec. 16, 2011 Stop & Shop [Member]	Feb. 28, 2011 Stop & Shop [Member]
Federal government deductible, percentage of balance of a covered loss		85.00%
Vornado deductible, annual aggregate			$ 180,000,000
Insurance limit per occurrence		2,000,000,000	180,000,000	2,000,000,000	300,000,000
Guarantees and master leases	266,074,000
Vornado deductible, percentage of property value			5.00%
Outstanding letters of credit	22,195,000
Commitment to fund additional capital to partially owned entities	259,607,000
Insurance deductible						3,200,000
Insurance Deductible Percentage Of Balance Of Covered Loss						15.00%
Commitments to Fund Improvements	11,500,000
Stop & Shop complaint regarding rent allocated to East Brunswick, Jersey City, Middletown, Union, and Woodbridge leases							5,000,000
Accounts Receivable, Gross							44,900,000
Loss Contingency, Opinion of Counsel	As a result of Stop & Shop appealing the Court’s decision, we believe, after consultation with counsel, that the maximum reasonably possible loss is up to the total amount of the receivable of $44,900,000.
Stop & Shop judgement in our favor to pay us the unpaid annual rent accrued									56,597,000	37,422,000
Stop & Shop recovery action of annual rent commenced by Vornado								2,500,000
Maximum Reasonably Possible Loss							$ 44,900,000