Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details) (USD $) In Thousands, unless otherwise specified	Dec. 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	$ 189,968		$ 155,522
Total acquisitions-related intangible liabilities, net	59,129	[1],[2]	36,587	[1],[2]
Deferred Leasing Costs [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	168,087		142,652
Accumulated amortization	(61,443)		(52,974)
Finite-lived intangible assets/liabilities, net	106,644		89,678
Above-Market Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	27,977		28,143
Accumulated amortization	(12,180)		(8,101)
Finite-lived intangible assets/liabilities, net	15,797		20,042
In-Place Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	101,061		61,355
Accumulated amortization	(34,019)		(15,753)
Finite-lived intangible assets/liabilities, net	67,042		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	690		200
Accumulated amortization	(205)		0
Finite-lived intangible assets/liabilities, net	485		200
Below-Market Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	70,486		37,582
Accumulated amortization	(17,555)		(6,158)
Finite-lived intangible assets/liabilities, net	52,931	[1]	31,424	[1]
Above-Market Ground Lease Obligation [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, Net
Finite-lived intangible assets/liabilities, gross	6,320		5,200
Accumulated amortization	(122)		(37)
Finite-lived intangible assets/liabilities, net	$ 6,198	[1]	$ 5,163	[1]

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

[2] See Note 4 for additional information.