Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Total deferred leasing costs and acquisition-related intangible assets, net	$ 158,132	[1]	$ 155,522
Total acquisitions-related intangible liabilities, net	45,055	[1],[2]	36,587	[2]
Deferred Leasing Costs [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	139,693		142,652
Accumulated amortization	(48,131)		(52,974)
Finite-lived intangible assets/liabilities, net	91,562	[1]	89,678
Above-Market Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	26,637		28,143
Accumulated amortization	(7,857)		(8,101)
Finite-lived intangible assets/liabilities, net	18,780		20,042
In-Place Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	63,465		61,355
Accumulated amortization	(15,825)		(15,753)
Finite-lived intangible assets/liabilities, net	47,640	[1]	45,602
Below Market Ground Lease Obligation [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	200		200
Accumulated amortization	(50)		0
Finite-lived intangible assets/liabilities, net	150		200
Below-Market Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	46,966		37,582
Accumulated amortization	(7,058)		(6,158)
Finite-lived intangible assets/liabilities, net	39,908	[1],[2]	31,424	[2]
Above-Market Ground Lease Obligation [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	5,200		5,200
Accumulated amortization	(53)		(37)
Finite-lived intangible assets/liabilities, net	$ 5,147	[2]	$ 5,163	[2]

[1] Balances and accumulated amortization amounts at March 31, 2012 reflect the write-off of the following fully amortized amounts at January 1, 2012: deferred leasing costs (approximately $9.5 million), above-market leases (approximately $1.6 million), in-place leases (approximately $3.7 million), and below-market leases (approximately $1.0 million).

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