Summary of Significant Accounting Policies - Operating Real Estate Estimated Useful Lives (Details)	9 Months Ended
	Sep. 30, 2020
Building (fee interest) | Minimum
Property, Plant and Equipment [Line Items]
Useful life (in years)	7 years
Building (fee interest) | Maximum
Property, Plant and Equipment [Line Items]
Useful life (in years)	48 years
Land improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful life (in years)	1 year
Land improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful life (in years)	15 years
Furniture, fixtures and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life (in years)	2 years
Furniture, fixtures and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life (in years)	8 years