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Debt - Schedule of Carrying Value of Debt (Details) - USD ($)	Dec. 31, 2024	Sep. 06, 2024	Sep. 05, 2024	May 02, 2024	May 01, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Total debt	$ 563,000,000					$ 1,700,000,000
Convertible Debt
Debt Instrument [Line Items]
Total convertible senior notes	418,000,000					1,607,000,000
2026 Notes \| Convertible Debt
Debt Instrument [Line Items]
Total convertible senior notes	0					496,000,000
2025 Notes \| Convertible Debt
Debt Instrument [Line Items]
Total convertible senior notes	418,000,000					504,000,000
2024 Notes \| Convertible Debt
Debt Instrument [Line Items]
Total convertible senior notes	0					607,000,000
Mortgages Segment
Debt Instrument [Line Items]
Total borrowings under credit facilities	145,000,000					93,000,000
Line of Credit
Debt Instrument [Line Items]
Total borrowings under credit facilities	145,000,000					93,000,000
Maximum borrowing capacity	300,000,000					250,000,000
UBS AG \| Line of Credit
Debt Instrument [Line Items]
Total borrowings under credit facilities	73,000,000
Maximum borrowing capacity	150,000,000	$ 150,000,000	$ 100,000,000			100,000,000
UBS AG \| Line of Credit \| Mortgages Segment
Debt Instrument [Line Items]
Total borrowings under credit facilities	73,000,000					45,000,000
JPMorgan Chase Bank, N.A. \| Line of Credit
Debt Instrument [Line Items]
Total borrowings under credit facilities	72,000,000
Maximum borrowing capacity	150,000,000			$ 150,000,000	$ 100,000,000	100,000,000
JPMorgan Chase Bank, N.A. \| Line of Credit \| Mortgages Segment
Debt Instrument [Line Items]
Total borrowings under credit facilities	72,000,000					40,000,000
Atlas Securitized Products, L.P. \| Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity						50,000,000
Atlas Securitized Products, L.P. \| Line of Credit \| Mortgages Segment
Debt Instrument [Line Items]
Total borrowings under credit facilities	$ 0					$ 8,000,000