Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 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	$ 36,202		$ 30,499		$ 17,987
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	20,804	[1]	16,905	[1]	13,344	[1]
Estimated annual amortization related to acquisition-related intangibles
2013	22,676
2014	20,235
2015	16,377
2016	13,757
2017	11,421
Thereafter	22,178
Finite-lived intangible assets/liabilities, net	106,644
Above 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	5,695	[2]	5,946	[2]	2,163	[2]
Estimated annual amortization related to acquisition-related intangibles
2013	5,316	[3]
2014	4,336	[3]
2015	2,533	[3]
2016	1,506	[3]
2017	1,185	[3]
Thereafter	921	[3]
Finite-lived intangible assets/liabilities, net	15,797	[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	21,976	[1]	12,575	[1]	3,266	[1]
Estimated annual amortization related to acquisition-related intangibles
2013	23,298
2014	15,567
2015	9,913
2016	6,798
2017	5,417
Thereafter	6,049
Finite-lived intangible assets/liabilities, net	67,042
Below-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	205	[4]	0	[4]	0	[4]
Estimated annual amortization related to acquisition-related intangibles
2013	8	[5]
2014	8	[5]
2015	8	[5]
2016	8	[5]
2017	8	[5]
Thereafter	445	[5]
Finite-lived intangible assets/liabilities, net	485	[5]
Below Market Leases [Member]
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization Of Intangible Liabilities	(12,393)	[6]	(4,890)	[6]	(786)	[6]
Estimated annual amortization related to acquisition-related intangibles
2013	13,140	[7]
2014	(11,360)	[7]
2015	(8,828)	[7]
2016	(6,645)	[7]
2017	(5,577)	[7]
Thereafter	(7,381)	[7]
Total	52,931	[7]
Leases Acquired In Place Above Market Ground Leases Adjustment Member
Amortization for the period related to deferred leasing costs and acquisition-related intangibles
Amortization Of Intangible Liabilities	(85)	[8]	(37)	[8]	0	[8]
Estimated annual amortization related to acquisition-related intangibles
2013	101	[9]
2014	(101)	[9]
2015	(101)	[9]
2016	(101)	[9]
2017	(101)	[9]
Thereafter	(5,693)	[9]
Total	$ 6,198	[9]

[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 periodspresented.

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

[3] Represents estimated annual amortization related to above-market operating leases. Amounts will be recorded as a decrease to rental income in the consolidated statements of operations.

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

[5] Represents estimated annual amortization related to below−market ground lease obligations. Amounts will be recorded as an increase to ground lease expense in the consolidated statements of operations.

[6] The amortization of below−market operating leases is recorded as an increase to rental income in the consolidated statements of operations for the periods presented.

[7] Represents estimated annual amortization related to below-market operating leases. Amounts will be recorded as an increase to rental income in the consolidated statements of operations.

[8] 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.

[9] Represents estimated annual amortization related to above−market ground lease obligations. Amounts will be recorded as a decrease to ground lease expense in the consolidated statements of operations.