Intangible Assets (Components of Intangible Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ 70,588	$ 53,483
Goodwill	1,674	1,674	$ 3,626	$ 3,647
Total intangible assets	240,770	245,529
In-place Leases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	182,908	185,251
Accumulated amortization	61,658	46,899
Above-market Tenant Leases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	37,914	40,260
Accumulated amortization	8,792	6,515
Below-market Ground Lease
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, net	18,274	18,344
Accumulated amortization	$ 138	$ 69