Mortgage Servicing Rights and Related Liabilities - Fair Value Sensitivity Analysis (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
10% Adverse Change	$ (157)	$ (165)
20% Adverse Change	(321)	(317)
Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
10% Adverse Change	44	46
20% Adverse Change	92	96
100 bps Adverse Change \| Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
Discount Rate	(87)	(127)
100 bps Adverse Change \| Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
Discount Rate	35	46
200 bps Adverse Change \| Mortgage servicing rights
Excess Spread Financing - Hypothetical Sensitivities
Discount Rate	(179)	(245)
200 bps Adverse Change \| Excess spread financing
Excess Spread Financing - Hypothetical Sensitivities
Discount Rate	$ 72	$ 95

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107314-111719

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- Definition

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.

+ References

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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

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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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