Deferred Leasing Costs and Acquisition-related Intangible Assets and Liabilities, net (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Total deferred leasing costs and acquisition-related intangible assets, net	$ 190,085		$ 189,968
Acquisition-related Intangible Liabilities, Net
Total acquisitions-related intangible liabilities, net	53,014	[1]	59,129	[1]
Deferred Leasing Costs [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	170,609		168,087
Finite-lived intangible assets accumulated amortization	(59,943)		(61,443)
Finite-lived intangible assets, net	110,666		106,644
Above-Market Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	28,842		27,977
Finite-lived intangible assets accumulated amortization	(14,038)		(12,180)
Finite-lived intangible assets, net	14,804	[2]	15,797
In-Place Leases [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	108,612		101,061
Finite-lived intangible assets accumulated amortization	(44,476)		(34,019)
Finite-lived intangible assets, net	64,136		67,042
Below Market Ground Lease Obligation [Member]
Deferred Leasing Costs and Acquisition-related Intangible Assets, Net
Finite-lived intangible assets, gross	490		690
Finite-lived intangible assets accumulated amortization	(11)		(205)
Finite-lived intangible assets, net	479	[3]	485
Below Market Lease [Member]
Acquisition-related Intangible Liabilities, Net
FiniteLivedIntangibleLiabilitiesGross	70,966		70,486
Accumulated amortization	(24,074)		(17,555)
Acquisition-related Intangible Liabilities, net	46,892	[1],[4]	52,931	[1]
Above-Market Ground Lease Obligation [Member]
Acquisition-related Intangible Liabilities, Net
FiniteLivedIntangibleLiabilitiesGross	6,320		6,320
Accumulated amortization	(198)		(122)
Acquisition-related Intangible Liabilities, net	$ 6,122	[1],[5]	$ 6,198	[1]

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

[2] 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.

[3] 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.

[4] 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.

[5] 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.