Loans Held for Sale - Fair Value - Schedule of Loans Held for Sale Fair Value (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Movement In Loans Held For Sale At Fair Value [Roll Forward]
Beginning balance	$ 2,048.3	$ 1,103.9	$ 1,290.2	$ 674.2
Originations and purchases	7,410.2	4,856.2	17,572.2	12,265.6
Proceeds from sales	(7,421.0)	(4,733.8)	(16,636.6)	(11,571.2)
Principal collections	(57.8)	(23.5)	(129.2)	(74.1)
Loans held for investment, at fair value	6.1	1.0	11.8	2.9
Receivables	(15.8)	(9.2)	(36.5)	(27.4)
REO (Other assets)	(15.9)	(8.2)	(41.3)	(15.5)
Advances (incl. capitalization upon Ginnie Mae modifications)	5.5	2.1	15.7	7.0
Fair value gain (loss) on loans held for sale, at fair value (1)	(48.6)	(0.1)	(157.5)	(82.3)
Other (2)	4.6	7.2	26.8	16.4
Ending balance	1,915.6	1,195.5	1,915.6	1,195.5
Principal amount outstanding on loans held for sale	2,001.2	1,401.2	2,001.2	1,401.2
Premium (discount) balance on loans held for sale	(69.0)	(91.6)	(69.0)	(91.6)
Fair value adjustment to loans held for sale	(16.6)	(19.4)	(16.6)	(19.4)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held-for-sale, Fair Value Disclosure	1,915.6	$ 1,195.5	1,915.6	$ 1,195.5
GSE loans
Movement In Loans Held For Sale At Fair Value [Roll Forward]
Beginning balance			610.8
Ending balance	605.4		605.4
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held-for-sale, Fair Value Disclosure	605.4		605.4
Government- Forward loans
Movement In Loans Held For Sale At Fair Value [Roll Forward]
Beginning balance			215.5
Ending balance	638.1		638.1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held-for-sale, Fair Value Disclosure	638.1		638.1
Repurchased Ginnie Mae Loans
Movement In Loans Held For Sale At Fair Value [Roll Forward]
Beginning balance			26.1
Ending balance	43.6		43.6
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held-for-sale, Fair Value Disclosure	43.6		43.6
Reverse Loans
Movement In Loans Held For Sale At Fair Value [Roll Forward]
Beginning balance			432.4
Ending balance	577.3		577.3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held-for-sale, Fair Value Disclosure	577.3		577.3
Other residential mortgage loans
Movement In Loans Held For Sale At Fair Value [Roll Forward]
Beginning balance			5.3
Ending balance	51.3		51.3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held-for-sale, Fair Value Disclosure	$ 51.3		$ 51.3

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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