Acquired Intangible Assets and Liabilities (Schedule of Estimated Annual Amortization Of Below Market Leases) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Net	$ 249,465	$ 81,899
Below-Market Leases, Net of Above Market Leases
Finite-Lived Intangible Assets [Line Items]
2018	(26,622)
2019	(15,372)
2020	(3,151)
2021	2,055
2022	9,054
Thereafter	99,126
Net	$ 65,090