Investments - Summary of Gross Investment Activity (Parenthetical) (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) Property	Mar. 31, 2018 USD ($) Property	Dec. 31, 2018 Property
Real Estate Properties [Line Items]
Number of property locations of investments | Property	708		665
Intangible lease liabilities		$ 12,000
Accumulated depreciation	$ 45,300,000	$ 20,400,000
Number of real estate properties acquired | Property	9
Loans receivable to purchaser of real estate property	$ 8,200,000
Property securitized by loan receivable carrying value	5,700,000
Property securitized by loan receivable	$ 3,400,000
Vacant Properties
Real Estate Properties [Line Items]
Number of property locations of investments | Property	1	3
Tenanted Properties
Real Estate Properties [Line Items]
Number of property locations of investments | Property	3	4