Investments - Summary of Remaining Weighted Average Amortization Period for Intangible Assets and Liabilities (Details)	6 Months Ended
	Jun. 30, 2018
Finite Lived Intangible Assets [Line Items]
Remaining weighted average amortization period, Intangible market lease liabilities	16 years 2 months 12 days
Total intangible assets and liabilities	11 years 8 months 12 days
In-place Leases
Finite Lived Intangible Assets [Line Items]
Remaining weighted average amortization period, In-place leases	11 years 3 months 18 days
Intangible Market Lease Assets
Finite Lived Intangible Assets [Line Items]
Remaining weighted average amortization period, Intangible assets	9 years