Fair Value Measurements - Level 3 Reconciliation (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Dec. 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	(132)	(190)
Payments received from borrowers		0
Purchases	0	469
Issuances	24	0
Sales		0
Settlements and repayments	(159)	(182)
Transfers to mortgage loans held for sale		0
Transfers to real estate owned		0
Balance - end of period	1,044	1,281
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	10	15
Payments received from borrowers		0
Purchases	0	0
Issuances	0	0
Sales		0
Settlements and repayments	0	0
Transfers to mortgage loans held for sale		0
Transfers to real estate owned		0
Balance - end of period	47	47
LPCs
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Derivative financial instruments	2		$ 3
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	(1,275)	(1,039)
Payments received from borrowers		0
Purchases	30	732
Issuances	412	298
Sales		(317)
Settlements and repayments	0	0
Transfers to mortgage loans held for sale		0
Transfers to real estate owned		0
Balance - end of period	2,663	3,339
IRLCs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	135
Total gains or losses included in earnings	279
Purchases	0
Issuances	0
Settlements and repayments	0
Balance - end of period	414
Mortgage loans held for investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period		119
Total gains or losses included in earnings		3
Payments received from borrowers		(11)
Purchases		0
Issuances		0
Sales		(94)
Settlements and repayments		0
Transfers to mortgage loans held for sale		12
Transfers to real estate owned		(5)
Balance - end of period		$ 0
LPCs
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	12
Total gains or losses included in earnings	26
Purchases	0
Issuances	0
Settlements and repayments	0
Balance - end of period	$ 38

Fair Value Measurement with Unobservable Inputs Reconciliation Recurring Basis, Asset, Payments From Borrowers

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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

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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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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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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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