Fair Value Measurements - Level 3 Reconciliation (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Excess spread financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	$ 934	$ 1,311
Total gains or losses included in earnings	41	(35)
Purchases	0	0
Issuances	0	24
Sales	0
Settlements and repayments	(41)	(58)
Balance - end of period	934	1,242
Mortgage servicing rights financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	33	37
Total gains or losses included in earnings	(10)	6
Purchases	0	0
Issuances	0	0
Sales	0
Settlements and repayments	0	0
Balance - end of period	23	43
LPCs
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	1
Total gains or losses included in earnings	37
Purchases	0
Issuances	0
Sales	0
Settlements and repayments	0
Balance - end of period	38
Forward mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	2,703	3,496
Total gains or losses included in earnings	298	(534)
Purchases	67	24
Issuances	288	123
Sales	(2)
Settlements and repayments	0	0
Balance - end of period	3,354	$ 3,109
IRLCs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	414
Total gains or losses included in earnings	(182)
Purchases	0
Issuances	0
Sales	0
Settlements and repayments	0
Balance - end of period	232
LPCs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	38
Total gains or losses included in earnings	(30)
Purchases	0
Issuances	0
Sales	0
Settlements and repayments	0
Balance - end of period	$ 8

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

+ References

No definition available.

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-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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-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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