Intangible Assets and Liabilities (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Amortizable intangible assets
Finite-lived intangible assets, gross	$ 616,653	$ 556,978
Less: accumulated amortization	(85,738)	(55,655)
Finite-lived intangible assets, net	530,915	501,323
Amortizable intangible liabilities
Finite-lived intangible liabilities, gross	(88,754)	(84,130)
Less: accumulated amortization	6,974	3,675
Finite-lived intangible liabilities, net	(81,780)	80,455
Below-market rent
Amortizable intangible liabilities
Finite-lived intangible liabilities, gross	(88,597)	(84,130)
Less: accumulated amortization	6,972	3,675
Finite-lived intangible liabilities, net	(81,625)	80,455
Above-market ground lease
Amortizable intangible liabilities
Finite-lived intangible liabilities, gross	(157)
Less: accumulated amortization	2
Finite-lived intangible liabilities, net	(155)
In-place lease
Amortizable intangible assets
Finite-lived intangible assets, gross	507,050	467,846
Less: accumulated amortization	(70,633)	(44,762)
Finite-lived intangible assets, net	436,417	423,084
Tenant relationship
Amortizable intangible assets
Finite-lived intangible assets, gross	13,361	13,231
Less: accumulated amortization	(4,183)	(3,307)
Finite-lived intangible assets, net	9,178	9,924
Above-market rent
Amortizable intangible assets
Finite-lived intangible assets, gross	89,118	74,491
Less: accumulated amortization	(10,875)	(7,584)
Finite-lived intangible assets, net	78,243	66,907
Below-market ground lease
Amortizable intangible assets
Finite-lived intangible assets, gross	7,124	1,410
Less: accumulated amortization	(47)	(2)
Finite-lived intangible assets, net	$ 7,077	$ 1,408