Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ 104,931	$ 53,483
Goodwill	1,674	1,674	$ 3,647
Total intangible assets	186,206	245,529
In-place leases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	139,548	185,251
Accumulated amortization	91,548	46,899
Above-market leases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	26,917	40,260
Accumulated amortization	13,038	6,515
Below-market ground leases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	18,067	18,344
Accumulated amortization	$ 345	$ 69