Intangible Assets and Liabilities (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Deferred financing and leasing costs, net	$ 85,168,000		$ 85,168,000		$ 85,001,000
Amortization of intangible assets and liabilities
Amortization of deferred financing costs	821,000	835,000	1,642,000	1,670,000
Amortization of deferred leasing costs and acquisition-related intangible assets (in depreciation and amortization)	4,401,000	3,817,000	8,757,000	7,583,000
Amortization of lease incentives (in rental and other revenues)	303,000	276,000	641,000	537,000
Amortization of acquisition-related intangible assets and liabilities (in rental and other revenues)	166,000	36,000	327,000	76,000
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Deferred financing costs (in years)	3.3		3.3
Amortization of deferred leasing costs and acquisition-related intangible assets (in depreciation and amortization) (in years)	6.1		6.1
Lease incentives (in rental and other revenues) (in years)	7.9		7.9
Amortization of acquisition-related intangible assets and liabilities (in rental and other revenues) (in years)	6.3		6.3
Intangible assets and liabilities from new acquisitions [Abstract]
Acquired above market lease intangible assets	100,000
Acquired in-place lease intangible assets	900,000
Weighted average amortization periods, above market (in years)	3.0		3.0
Weighted average amortization periods, in-place (in years)	3.0		3.0
Deferred Financing Costs [Member]
Finite-Lived Intangible Assets [Line Items]
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, gross	17,295,000		17,295,000		16,412,000
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, accumulated amortization	(7,996,000)		(7,996,000)		(7,054,000)
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, net	9,299,000		9,299,000		9,358,000
Deferred Leasing Costs [Member]
Finite-Lived Intangible Assets [Line Items]
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, gross	130,415,000		130,415,000		127,949,000
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, accumulated amortization	(54,546,000)		(54,546,000)		(52,306,000)
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, net	75,869,000		75,869,000		75,643,000
Acquisition-Related Intangible Liabilities [Member]
Finite-Lived Intangible Assets [Line Items]
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, gross	720,000		720,000		658,000
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, accumulated amortization	(226,000)		(226,000)		(125,000)
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, net	494,000		494,000		533,000
Acquisition Related Intangible Assets and Liabilities Amortization Recorded in Rental and Other Revenues [Member]
Scheduled future amortization of intangible assets and liabilities
July 1, 2011 through December 31, 2011			320,000
2012			561,000
2013			390,000
2014			298,000
2015			188,000
Thereafter			471,000
Total future amortization of intangible assets and liabilities			2,228,000
Deferred Financing Costs Amortization Recorded in Interest Expense[Member]
Scheduled future amortization of intangible assets and liabilities
July 1, 2011 through December 31, 2011			1,724,000
2012			3,093,000
2013			1,486,000
2014			1,098,000
2015			1,098,000
Thereafter			800,000
Total future amortization of intangible assets and liabilities			9,299,000
Deferred Leasing Costs and Acquisition-Related Intangible Assets Amortization Recorded in Depreciation and Amortization [Member]
Scheduled future amortization of intangible assets and liabilities
July 1, 2011 through December 31, 2011			8,653,000
2012			15,087,000
2013			12,106,000
2014			9,398,000
2015			6,966,000
Thereafter			14,690,000
Total future amortization of intangible assets and liabilities			66,900,000
Lease Incentives Amortization Recorded in Rental and Other Revenues [Member]
Scheduled future amortization of intangible assets and liabilities
July 1, 2011 through December 31, 2011			613,000
2012			1,141,000
2013			983,000
2014			819,000
2015			603,000
Thereafter			2,088,000
Total future amortization of intangible assets and liabilities			$ 6,247,000