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Area of a real estate property.

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The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes.

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Properties - Narrative (Details) ft² in Millions	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
Properties - Narrative (Details) ft² in Millions	Sep. 30, 2017 ft² property	Sep. 30, 2023 USD ($) property residential_unit	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) property residential_unit	Sep. 30, 2022 USD ($) property	Dec. 31, 2016 ft² building
Real Estate Properties [Line Items]
Property impairment loss				$ 23,800,000
Operating Properties \| Commercial and Residential Lending Segment \| Montgomery Alabama
Real Estate Properties [Line Items]
Proceeds from sale of operating properties					$ 114,800,000
Gain on sale of property					$ 86,600,000
Operating Properties \| Investing and Servicing Segment
Real Estate Properties [Line Items]
Number of properties sold \| property		2		3	2
Proceeds from sale of operating properties		$ 34,600,000	$ 19,500,000	$ 50,900,000	$ 54,000,000
Gain on sale of property		10,600,000	13,700,000	15,400,000	25,400,000
Gain on sale of property attributable to noncontrolling interest					$ 600,000
Residential Units \| Commercial and Residential Lending Segment
Real Estate Properties [Line Items]
Proceeds from sale of operating properties		9,100,000		12,100,000
Gain on sale of property		$ 0		$ 0
Number of residential units sold \| residential_unit		3		4
Medical Office Portfolio
Real Estate Properties [Line Items]
Number of acquired properties closed \| building						34
Area of property \| ft²						1.9
Total gross properties and lease intangibles		$ 776,400,000		$ 776,400,000
Debt		597,900,000		597,900,000
Master Lease Portfolio
Real Estate Properties [Line Items]
Total gross properties and lease intangibles		343,800,000		343,800,000
Debt		193,600,000		193,600,000
Number of retail properties acquired \| property	16
Number of square feet of properties \| ft²	1.9
Term of master lease agreements	24 years 7 months 6 days
Master Lease Portfolio \| Minimum \| Retail Properties \| Geographic Concentration Risk \| Utah, Florida, Texas and Minnesota
Real Estate Properties [Line Items]
Concentration risk (as a percent)	50.00%
REIS Equity Portfolio
Real Estate Properties [Line Items]
Total gross properties and lease intangibles		142,900,000		142,900,000
Debt		$ 93,100,000		$ 93,100,000
Number of retail properties acquired \| property				7
REIS Equity Portfolio \| Operating Properties
Real Estate Properties [Line Items]
Number of properties sold \| property		2		3	2
Proceeds from sale of operating properties		$ 34,600,000	19,500,000	$ 50,900,000	$ 54,000,000
Gain on sale of property		10,600,000	$ 13,700,000	15,400,000	$ 25,400,000
Commercial and Residential Lending Segment Property Portfolio
Real Estate Properties [Line Items]
Total gross properties and lease intangibles		494,400,000		494,400,000
Debt		$ 204,400,000		$ 204,400,000