Real Estate Asset Acquisitions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) property	Sep. 30, 2020 USD ($)
Real Estate [Line Items]
Total assets	$ 2,084.3	$ 2,114.9
Total liabilities	$ 949.3	$ 998.3
Weighted average amortization period of unfavorable leases	18 years 7 months 6 days
In-place lease
Real Estate [Line Items]
Weighted-average amortization period of in-place/favorable leases	8 years 2 months 12 days
Unfavorable leases
Real Estate [Line Items]
Weighted-average amortization period of in-place/favorable leases	4 years 8 months 12 days
2019 Acquisitions
Real Estate [Line Items]
Number of commercial real estate assets purchased | property	5
Purchase consideration	$ 218.4
Land	106.9
Property and improvements	91.3
In-place leases	23.2
Favorable leases	4.3
Total assets	225.7
Unfavorable leases	7.3
Total liabilities	7.3
Net assets acquired	$ 218.4