Fair Value Measurements - Level 3 Reconciliation (Details) - USD ($) $ in Millions	2 Months Ended	7 Months Ended	9 Months Ended
Sep. 30, 2018	Jul. 31, 2018	Sep. 30, 2019
Excess spread financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	$ 1,039		$ 1,184
Total gains or losses included in earnings	26		(190)
Payments received from borrowers	0		0
Purchases	0		0
Issuances	84		469
Sales	0		0
Repayments	(21)		(19)
Settlements	(31)		(163)
Balance - end of period	1,097	$ 1,039	1,281
Mortgage servicing rights financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	26		32
Total gains or losses included in earnings	0		15
Payments received from borrowers	0		0
Purchases	0		0
Issuances	0		0
Sales	0		0
Repayments	0		0
Settlements	0		0
Balance - end of period	26	26	47
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	3,413		3,665
Total gains or losses included in earnings	20		(1,039)
Payments received from borrowers	0		0
Purchases	72		732
Issuances	43		298
Sales	(63)		(317)
Repayments	0		0
Settlements	0		0
Transfers to mortgage loans held for sale			0
Transfers to real estate owned			0
Balance - end of period	3,485	3,413	3,339
Mortgage loans held for investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	125		119
Total gains or losses included in earnings	(1)		3
Payments received from borrowers	(2)		(11)
Purchases	0		0
Issuances	0		0
Sales	0		(94)
Repayments	0		0
Settlements	0		0
Transfers to mortgage loans held for sale			(12)
Transfers to real estate owned			(5)
Balance - end of period	122	125	$ 0
Nationstar Mortgage Holdings Inc. \| Excess spread financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	1,039	996
Total gains or losses included in earnings		81
Purchases		0
Issuances		70
Sales		0
Repayments		(3)
Settlements		(105)
Balance - end of period		1,039
Nationstar Mortgage Holdings Inc. \| Mortgage servicing rights financing
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	26	10
Total gains or losses included in earnings		16
Purchases		0
Issuances		0
Sales		0
Repayments		0
Settlements		0
Balance - end of period		26
Nationstar Mortgage Holdings Inc. \| Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance - beginning of period	$ 3,413	2,937
Total gains or losses included in earnings		166
Purchases		144
Issuances		162
Sales		4
Repayments		0
Settlements		0
Balance - end of period		$ 3,413

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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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 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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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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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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