Intangible Assets and Liabilities - Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Intangible Assets [Line Items]
Intangible Assets, Total Cost	$ 194,509	$ 196,417
Intangible Assets, Accumulated Amortization	(74,606)	(65,069)
Intangible Assets, net	119,903	131,348
Acquired Lease Intangibles, Net	29,813	31,783
Below market leases [Member]
Intangible Assets [Line Items]
Acquired Lease Intangibles, Gross	49,228	49,655
Acquired Lease Intangibles, Accumulated Amortization	(19,415)	(17,872)
Acquired Lease Intangibles, Net	29,813	31,783
In-place lease value [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	179,979	181,887
Intangible Assets, Accumulated Amortization	(62,584)	(53,376)
Intangible Assets, net	117,395	128,511
Tenant relationship value [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	9,564	9,564
Intangible Assets, Accumulated Amortization	(8,715)	(8,551)
Intangible Assets, net	849	1,013
Above market leases acquired [Member]
Intangible Assets [Line Items]
Intangible Assets, Total Cost	4,966	4,966
Intangible Assets, Accumulated Amortization	(3,307)	(3,142)
Intangible Assets, net	$ 1,659	$ 1,824