Intangible Assets and Liabilities (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Deferred financing and leasing costs, net	$ 129,311,000		$ 129,311,000		$ 85,001,000
Amortization of intangible assets and liabilities [Abstract]
Amortization of deferred financing costs	806,000	858,000	2,448,000	2,528,000
Amortization of deferred leasing costs and acquisition-related intangible assets (in depreciation and amortization)	5,188,000	3,912,000	13,945,000	11,495,000
Amortization of lease incentives (in rental and other revenues)	368,000	270,000	1,009,000	807,000
Amortization of acquisition-related intangible assets (in rental and other revenues)	240,000	200,000	618,000	318,000
Amortization of acquisition-related intangible liabilities (in rental and other revenues)	(229,000)	(27,000)	(280,000)	(69,000)
Weighted average remaining amortization periods for intangible assets and liabilities [Abstract]
Deferred financing costs (in years)	3.9		3.9
Amortization of deferred leasing costs and acquisition-related intangible assets (in depreciation and amortization) (in years)	6.4		6.4
Lease incentives (in rental and other revenues) (in years)	8.1		8.1
Amortization of acquisition-related intangible assets (in rental and other revenues) (in years)	5.8		5.8
Amortization of acquisition-related intangible liabilities (in rental and other revenues) (in years)	8.8		8.8
Intangible assets and liabilities from new acquisitions [Abstract]
Acquired above market lease intangible assets	1,600
Acquired in-place lease intangible assets	38,100
Assumed below market lease intangible liabilities	15,600
Weighted average amortization periods, above market (in years)	5.4		5.4
Weighted average amortization periods, in-place (in years)	6.7		6.7
Weighted average amortization periods, below market (in years)	8.8		8.8
Deferred Financing Costs [Member]
Finite-Lived Intangible Assets [Line Items]
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, gross	19,168,000		19,168,000		16,412,000
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, accumulated amortization	(6,192,000)		(6,192,000)		(7,054,000)
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, net	12,976,000		12,976,000		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	171,093,000		171,093,000		127,949,000
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, accumulated amortization	(54,758,000)		(54,758,000)		(52,306,000)
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, net	116,335,000		116,335,000		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	16,455,000		16,455,000		658,000
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, accumulated amortization	(425,000)		(425,000)		(125,000)
Deferred financing costs, deferred leasing costs and acquisition-related intangible liabilities, net	16,030,000		16,030,000		533,000
Acquisition Related Intangible Assets Amortization Recorded in Rental and Other Revenues [Member]
Scheduled future amortization of intangible assets and liabilities
October 1, 2011 through December 31, 2011			271,000
2012			1,049,000
2013			802,000
2014			505,000
2015			335,000
Thereafter			1,103,000
Total future amortization of intangible assets and liabilities			4,065,000
Acquisition Related Intangible Liabilities Amortization Recorded in Rental and Other Revenues [Member]
Scheduled future amortization of intangible assets and liabilities
October 1, 2011 through December 31, 2011			(141,000)
2012			(556,000)
2013			(542,000)
2014			(467,000)
2015			(421,000)
Thereafter			(13,903,000)
Total future amortization of intangible assets and liabilities			(16,030,000)
Deferred Financing Costs Amortization Recorded in Interest Expense[Member]
Scheduled future amortization of intangible assets and liabilities
October 1, 2011 through December 31, 2011			931,000
2012			3,192,000
2013			2,956,000
2014			2,660,000
2015			2,064,000
Thereafter			1,173,000
Total future amortization of intangible assets and liabilities			12,976,000
Deferred Leasing Costs and Acquisition-Related Intangible Assets Amortization Recorded in Depreciation and Amortization [Member]
Scheduled future amortization of intangible assets and liabilities
October 1, 2011 through December 31, 2011			6,263,000
2012			22,604,000
2013			17,849,000
2014			13,609,000
2015			9,950,000
Thereafter			35,214,000
Total future amortization of intangible assets and liabilities			105,489,000
Lease Incentives Amortization Recorded in Rental and Other Revenues [Member]
Scheduled future amortization of intangible assets and liabilities
October 1, 2011 through December 31, 2011			323,000
2012			1,234,000
2013			1,080,000
2014			913,000
2015			695,000
Thereafter			2,536,000
Total future amortization of intangible assets and liabilities			$ 6,781,000