Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details 1) (USD $) In Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	$ 7,833		$ 5,770		$ 21,831		$ 11,760
Deferred Leasing Costs [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	4,317	[1]	3,886	[1]	12,053	[1]	9,559	[1]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2011					4,748
2012					17,689
2013					15,823
2014					13,796
2015					10,387
Thereafter					25,641
Total					88,084
Net Above (Below)-Market Leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	121	[2]	664	[2]	1,519	[2]	696	[2]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2011					(78)	[3]
2012					(1,534)	[3]
2013					(1,690)	[3]
2014					(1,339)	[3]
2015					(790)	[3]
Thereafter					(4,684)	[3]
Total					(10,115)	[3]
In-Place Leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	3,379	[1]	1,220	[1]	8,238	[1]	1,505	[1]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2011					3,643
2012					12,863
2013					10,578
2014					7,830
2015					4,366
Thereafter					6,500
Total					45,780
Above-Market Ground Lease Obligation [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization for the period related to deferred leasing costs and acquisition-related intangibles	16	[4]	0	[4]	21	[4]	0	[4]
Estimated annual amortization related to acquisition-related intangibles
Remaining 2011					16
2012					63
2013					63
2014					63
2015					63
Thereafter					4,911
Total					$ 5,179

[1] The amortization of deferred leasing costs and in-place leases is recorded to depreciation and amortization expense in the consolidated statements of operations for the periods presented.

[2] he amortization of net above-market leases is recorded as a decrease to rental income in the consolidated statements of operations for the periods presented.

[3] Represents estimated annual net amortization related to above-/(below)-market leases. Amounts shown represent net below-market leases which will be recorded as an increase to rental income in the consolidated statements of operations.

[4] The amortization of the above-market ground lease obligation is recorded as a decrease to ground lease expense in the consolidated statements of operations for the periods presented.