Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Total deferred leasing costs and acquisition-related intangible assets, net	$ 196,525	[1]	$ 189,968
Acquisition-related Intangible Liabilities, Net
Total acquisitions-related intangible liabilities, net	57,188	[1],[2]	59,129	[2]
Deferred Leasing Costs [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	171,107		168,087
Finite-lived intangible assets accumulated amortization	(62,265)		(61,443)
Finite-lived intangible assets, net	108,842	[1]	106,644
Above-Market Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	27,627		27,977
Finite-lived intangible assets accumulated amortization	(13,010)		(12,180)
Finite-lived intangible assets, net	14,617	[3]	15,797
In-Place Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	103,778		101,061
Finite-lived intangible assets accumulated amortization	(31,195)		(34,019)
Finite-lived intangible assets, net	72,583	[1]	67,042
Below Market Ground Lease Obligation [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	690		690
Finite-lived intangible assets accumulated amortization	(207)		(205)
Finite-lived intangible assets, net	483	[4]	485
Below Market Leases [Member]
Acquisition-related Intangible Liabilities, Net
FiniteLivedIntangibleLiabilitiesGross	67,705		70,486
Accumulated amortization	(16,690)		(17,555)
Acquisition-related Intangible Liabilities, net	51,015	[1],[2],[5]	52,931	[2]
Above-Market Ground Lease Obligation [Member]
Acquisition-related Intangible Liabilities, Net
FiniteLivedIntangibleLiabilitiesGross	6,320		6,320
Accumulated amortization	(147)		(122)
Acquisition-related Intangible Liabilities, net	$ 6,173	[2],[6]	$ 6,198	[2]

[1] Balances and accumulated amortization amounts at March 31, 2013 reflect the write-off of the following fully amortized amounts at January 1, 2013: deferred leasing costs (approximately $7.0 million), above-market leases (approximately $0.6 million), in-place leases (approximately $10.3 million), and below-market leases (approximately $4.4 million).

[2] Included in deferred revenue and acquisition-related intangible liabilities, net in the consolidated balance sheets.

[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] 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.

[5] 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.

[6] 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.