Fair Value Measurements - Level 3 Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Excess spread financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	$ 1,311	$ 1,184
Total gains or losses included in earnings	(35)	(69)
Payments received from borrowers		0
Purchases	0	0
Issuances	24	245
Sales		0
Settlements	(58)	(51)
Balance - end of period	1,242	1,309
Mortgage servicing rights financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	37	32
Total gains or losses included in earnings	6	2
Payments received from borrowers		0
Purchases	0	0
Issuances	0	0
Sales		0
Settlements	0	0
Balance - end of period	43	34
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	3,496	3,665
Total gains or losses included in earnings	(534)	(399)
Payments received from borrowers		0
Purchases	24	409
Issuances	123	66
Sales		(260)
Settlements	0	0
Balance - end of period	$ 3,109	$ 3,481

Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Asset, Payments Received

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- Definition

Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Liability, Payments Received

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No definition available.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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-Publisher FASB
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-SubTopic 10
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Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sales of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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