Investments - Summary of Gross Investment Activity, Footnotes (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) Property	Sep. 30, 2020 USD ($) Property	Dec. 31, 2019 Property
Real Estate Properties [Line Items]
Number of real estate properties acquired	10
Loans receivable to purchaser of real estate property | $	$ 11.8
Loans receivable carrying value | $	9.2
Number of property locations of investments		1,096	1,000
Accumulated depreciation | $	$ 62.0	$ 103.1
Vacant Properties
Real Estate Properties [Line Items]
Number of property locations of investments	1	8
Tenanted Properties
Real Estate Properties [Line Items]
Number of property locations of investments	5	6