Intangible Assets and Liabilities - Intangible Assets and Liabilities Summary (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 732,783	$ 740,965
Less: accumulated amortization	(264,330)	(245,900)
Finite-lived intangible assets, net	468,453	495,065
Indefinite-Lived Intangible Assets
Goodwill	304	304
Total intangible assets, gross	733,087	741,269
Total intangible assets, net	468,757	495,369
Finite-Lived Intangible Liabilities
Finite-lived intangible liabilities, gross	(82,892)	(83,404)
Less: accumulated amortization	23,932	22,182
Finite-lived intangible liabilities, net	(58,960)	(61,222)
Below-market rent
Finite-Lived Intangible Liabilities
Finite-lived intangible liabilities, gross	(81,747)	(82,259)
Less: accumulated amortization	23,865	22,121
Finite-lived intangible liabilities, net	$ (57,882)	(60,138)
Below-market rent | Minimum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	7 years
Below-market rent | Maximum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	53 years
Above-market ground lease
Finite-Lived Intangible Liabilities
Finite-lived intangible liabilities, gross	$ (1,145)	(1,145)
Less: accumulated amortization	67	61
Finite-lived intangible liabilities, net	$ (1,078)	(1,084)
Above-market ground lease | Minimum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	49 years
Above-market ground lease | Maximum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	88 years
In-place lease
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 623,441	629,961
Less: accumulated amortization	(229,845)	(213,641)
Finite-lived intangible assets, net	$ 393,596	416,320
In-place lease | Minimum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	4 years
In-place lease | Maximum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	53 years
Above-market rent
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 96,656	98,162
Less: accumulated amortization	(33,643)	(31,533)
Finite-lived intangible assets, net	$ 63,013	66,629
Above-market rent | Minimum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	7 years
Above-market rent | Maximum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	40 years
Below-market ground leases and other
Finite-Lived Intangible Assets
Finite-lived intangible assets, gross	$ 12,686	12,842
Less: accumulated amortization	(842)	(726)
Finite-lived intangible assets, net	$ 11,844	$ 12,116
Below-market ground leases and other | Minimum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	55 years
Below-market ground leases and other | Maximum
Intangible Assets Liabilities
Finite lived intangible asset/liability, useful life	94 years