Basis of Presentation and Significant Accounting Policies (Details 2) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Impairment
Non-cash impairment charges	$ 8,300,000	$ 82,000,000	$ 25,086,000	$ 88,986,000
Accounts receivable
Straight-line rental revenue receivable	101,179,000		101,179,000		94,541,000
Tenant receivables	11,808,000		11,808,000		11,933,000
Non-tenant receivables	542,000		542,000		938,000
Allowance for doubtful accounts	(2,900,000)		(2,900,000)		(1,459,000)
Accounts receivable	110,629,000		110,629,000		105,953,000
Deferred Financing Fees, net
Deferred financing fees, net of accumulated amortization	16,663,000		16,663,000		22,579,000
Accumulated amortization of deferred financing fees	18,400,000		18,400,000		14,100,000
Other Intangible Assets
Lease intangibles, net	213,547,000		213,547,000		253,630,000
Revenue Recognition
Net increase in rental revenues due to straight-line rent adjustments	2,600,000	6,700,000	13,700,000	17,900,000
Net increase in rental revenues due to amortization of acquired above and below market leases	3,400,000	2,900,000	9,411,000	15,400,000
Lease termination fees recognized	200,000	800,000	1,200,000	6,400,000
Other Intangible Assets
Other Intangible Assets
Cost	4,422,000		4,422,000		2,977,000
Less: accumulated depreciation and amortization	(609,000)		(609,000)		(476,000)
Lease intangibles, net	3,813,000		3,813,000		2,501,000
Anticipated amortization associated with other intangible assets for each of the following five years
October - December 2012	157,000		157,000
2013	629,000		629,000
2014	629,000		629,000
2015	374,000		374,000
2016	$ 119,000		$ 119,000