Mortgage Servicing Rights and Related Liabilities - Fair Value Sensitivity Analysis (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
Total prepayment speeds, 10% Adverse Change	$ (179)	$ (136)
Total prepayment speeds, 20% Adverse Change	(348)	(264)
Cost to Service per Loan, 10% Adverse Change	(80)	(61)
Cost to Service per Loan, 20% Adverse Change	(159)	(122)
Mortgage servicing rights \| 100 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)	(341)
Mortgage servicing rights \| 200 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)	(655)
Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
Total prepayment speeds, 10% Adverse Change	9	11
Total prepayment speeds, 20% Adverse Change	17	22
Excess spread financing \| 100 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)	15
Excess spread financing \| 200 bps Adverse Change
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)	$ 32
100 bps Adverse Change \| Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)		(266)
100 bps Adverse Change \| Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)		19
200 bps Adverse Change \| Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)		(511)
200 bps Adverse Change \| Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
Option Adjusted Spread(1)		$ 40

The hypothetical financial impact of a 10 percent adverse change of the specified assumption on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481326/860-20-50-4

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The hypothetical financial impact of a 10 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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The hypothetical financial impact of a 20 percent adverse change of the specified assumption on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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The hypothetical financial impact of a 20 percent adverse change of prepayment speed on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481326/860-20-50-4

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The hypothetical financial impact of a specified adverse percentage change in discount rate on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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