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Properties - Narrative (Details) ft² in Millions	1 Months Ended	12 Months Ended
Properties - Narrative (Details) ft² in Millions	Sep. 30, 2017 ft² property	Dec. 31, 2023 USD ($) property residential_unit	Dec. 31, 2022 USD ($) property	Dec. 31, 2021 USD ($) property	Dec. 31, 2016 ft² building
Real Estate Properties [Line Items]
Property impairment loss		$ 124,900,000
Operating Properties \| Investing and Servicing Segment
Real Estate Properties [Line Items]
Number of properties sold \| property		4	3	2
Proceeds from sale of operating properties		$ 63,700,000	$ 92,100,000	$ 68,700,000
Gain on sale of property		25,600,000	50,900,000	22,200,000
Deconsolidation of subsidiary		10,200,000
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		12,100,000
Gain on sale of property		$ 0
Number of residential units sold \| residential_unit		4
California
Real Estate Properties [Line Items]
Property impairment loss		$ 94,800,000
Texas
Real Estate Properties [Line Items]
Property impairment loss		30,100,000
Montgomery Alabama \| Operating Properties \| Commercial and Residential Lending Segment
Real Estate Properties [Line Items]
Proceeds from sale of operating properties			114,800,000	31,200,000
Gain on sale of property			86,600,000	17,700,000
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		778,200,000
Debt		598,400,000
Master Lease Portfolio
Real Estate Properties [Line Items]
Total gross properties and lease intangibles		343,800,000
Debt		193,700,000
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
Depreciation		290,900,000
Non-controlling interest income		11,700,000	$ 9,700,000	$ 9,000,000
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		109,500,000
Debt		$ 68,800,000
Number of retail properties acquired \| property		6
REIS Equity Portfolio \| Operating Properties
Real Estate Properties [Line Items]
Number of properties sold \| property		4	3	2
Proceeds from sale of operating properties		$ 63,700,000	$ 92,100,000	$ 68,700,000
Gain on sale of property		25,600,000	$ 50,900,000	$ 22,200,000
Commercial And Residential Lending Segment Property Portfolio
Real Estate Properties [Line Items]
Total gross properties and lease intangibles		456,500,000
Debt		$ 234,900,000