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Fair Value - Schedule of Fair Value Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Loans held for sale, at fair value (a) (d)
Loans held for sale, at fair value	$ 1,915.6	$ 2,048.3	$ 1,290.2	$ 1,195.5	$ 1,103.9	$ 674.2
Financial liabilities
Advance match funded liabilities	320.6		417.1
Financing liabilities, at fair value:
HMBS-related borrowings	9,924.6	10,253.1	10,872.1	8,132.5	8,035.4	7,797.3
Other financing liabilities, at fair value	822.0		846.9
Other secured borrowings:
Mortgage loan financing facilities, net ($613.9 and $481.9 related to VIEs)	2,062.3		1,528.2
MSR financing facilities	1,223.2		957.9
Senior notes
Senior notes (b) (c)	489.0		487.4
Mortgage servicing rights
MSRs	2,762.9	2,632.6	2,466.3		2,327.7	2,272.2
Carrying Value
Loans held for sale, at fair value (a) (d)
Loans held for sale, at fair value	1,915.6		1,290.2
Financing liabilities, at fair value:
Other financing liabilities, at fair value	822.0		846.9
Fair Value
Loans held for sale, at fair value (a) (d)
Loans held for sale, at fair value	1,915.6		1,290.2
Financing liabilities, at fair value:
Other financing liabilities, at fair value	822.0		846.9
Financing Liability Excess Servicing Spread [Member]
Financing liabilities, at fair value:
Other financing liabilities, at fair value	255.3		263.3
Level 3 | Carrying Value
Loans held for sale, at fair value (a) (d)
Loans held for investment, at fair value (a)	10,117.4		11,125.3
Advances, net	435.1		577.2
Receivables, net	167.4		176.4
Financial liabilities
Advance match funded liabilities	320.6		417.1
Financing liabilities, at fair value:
HMBS-related borrowings	9,924.6		10,872.1
Other secured borrowings:
Mortgage loan financing facilities, net ($613.9 and $481.9 related to VIEs)	2,062.3		1,528.2
MSR financing facilities	1,223.2		957.9
Mortgage servicing rights
MSRs	2,762.9		2,466.3
Level 3 | Fair Value
Loans held for sale, at fair value (a) (d)
Loans held for investment, at fair value (a)	10,117.4		11,125.3
Advances, net	435.1		577.2
Receivables, net	167.4		176.4
Financial liabilities
Advance match funded liabilities	320.6		417.1
Financing liabilities, at fair value:
HMBS-related borrowings	9,924.6		10,872.1
Other secured borrowings:
Mortgage loan financing facilities, net ($613.9 and $481.9 related to VIEs)	2,067.4		1,535.3
MSR financing facilities	1,215.5		947.6
Mortgage servicing rights
MSRs	2,762.9		2,466.3
Level 3 | Interest Rate Contract | Carrying Value
Derivative financial instrument assets (liabilities), net
Interest rate lock commitments	12.6		(0.5)
Level 3 | Interest Rate Contract | Fair Value
Derivative financial instrument assets (liabilities), net
Interest rate lock commitments	12.6		(0.5)
Level 3 | Loans Held for Sale - Fair Value
Mortgage servicing rights
Loans related to Ginnie Mae guaranteed securitizations	636.7	$ 544.2	472.9	$ 446.5	$ 296.7	$ 203.1
Level 2 | Carrying Value
Senior notes
Senior notes (b) (c)	489.0		487.4
Level 2 | Fair Value
Senior notes
Senior notes (b) (c)	502.5		495.0
Level 1 | Other | Carrying Value
Derivative financial instrument assets (liabilities), net
Interest rate lock commitments	(21.1)		(11.7)
Level 1 | Other | Fair Value
Derivative financial instrument assets (liabilities), net
Interest rate lock commitments	$ (21.1)		$ (11.7)

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents advances and match funded advances.

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Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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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Amount of borrowings classified as other, maturing within one year or the normal operating cycle, if longer.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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