Investments - Schedule of Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	$ 64,315	$ 62,453
Intangible assets, Accumulated Amortization	11,186	9,432
Intangible assets, Net Carrying Amount	53,129	53,021
Intangible market lease liabilities, Gross Carrying Amount	14,748	14,824
Intangible market lease liabilities, Accumulated Amortization	2,596	2,503
Intangible market lease liabilities, Net Carrying Amount	12,152	12,321
In-place Leases
Finite Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	47,556	44,738
Intangible assets, Accumulated Amortization	7,655	6,638
Intangible assets, Net Carrying Amount	39,901	38,100
Intangible Market Lease Assets
Finite Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	16,759	17,715
Intangible assets, Accumulated Amortization	3,531	2,794
Intangible assets, Net Carrying Amount	$ 13,228	$ 14,921