Intangible Assets and Liabilities - Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Intangible Assets [Line Items]
Intangible assets, total cost	$ 179,104	$ 196,417
Intangible assets, accumulated amortization	(83,306)	(65,069)
Intangible assets, net	95,798	131,348
Acquired lease intangibles, net	24,050	31,783
In-place lease value
Intangible Assets [Line Items]
Intangible assets, total cost	168,881	181,887
Intangible assets, accumulated amortization	(74,951)	(53,376)
Intangible assets, net	93,930	128,511
Tenant relationship value
Intangible Assets [Line Items]
Intangible assets, total cost	5,268	9,564
Intangible assets, accumulated amortization	(4,728)	(8,551)
Intangible assets, net	540	1,013
Above market leases acquired
Intangible Assets [Line Items]
Intangible assets, total cost	4,955	4,966
Intangible assets, accumulated amortization	(3,627)	(3,142)
Intangible assets, net	1,328	1,824
Below market leases acquired
Intangible Assets [Line Items]
Acquired lease intangibles, gross	44,876	49,655
Acquired lease intangibles, accumulated amortization	(20,826)	(17,872)
Acquired lease intangibles, net	$ 24,050	$ 31,783