Intangible Assets and Liabilities - Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Intangible Assets [Line Items]
Intangible Assets, Total Cost	$ 116,523	$ 160,681
Intangible Assets, Accumulated Amortization	(57,113)	(88,203)
Intangible Assets, net	59,410	72,478
Acquired Lease Intangibles, Net	15,989	18,119
Below market leases [Member]
Intangible Assets [Line Items]
Acquired Lease Intangibles, Gross	30,391	37,579
Acquired Lease Intangibles, Accumulated Amortization	(14,402)	(19,460)
Acquired Lease Intangibles, Net	15,989	18,119
In-place lease value [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	99,338	142,889
Intangible Assets, Accumulated Amortization	(44,364)	(75,696)
Intangible Assets, net	54,974	67,193
Tenant relationship value [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	12,831	13,074
Intangible Assets, Accumulated Amortization	(10,412)	(10,167)
Intangible Assets, net	2,419	2,907
Above market leases acquired [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	4,354	4,718
Intangible Assets, Accumulated Amortization	(2,337)	(2,340)
Intangible Assets, net	$ 2,017	$ 2,378