Mortgage Loans Held for Sale - Reconciliation to Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Mortgage Loans Held for Sale
Balance - beginning of period	$ 2,211	$ 927
Loans sold (at carrying value) and loan payments received	(8,535)	(3,186)
Mortgage loans originated and purchased, net of fees	8,353	2,942
Repurchase of loans out of Ginnie Mae securitizations(1)	545	386
Net change in unrealized gain on retained loans held for sale	30	3
Net transfers of mortgage loans held for sale(2)	(1)	(2)
Balance - end of period	$ 2,603	$ 1,070

Loans Receivable Held-for-sale, Reconciliation to Cash Flow, Changes in Fair Value

No definition available.

Name:	coop_LoansReceivableHeldforsaleReconciliationtoCashFlowChangesinFairValue
Namespace Prefix:	coop_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loans Receivable Held-for-sale, Reconciliation to Cash Flow, Transfer from Held-for-sale to Held For Investment or Other Assets

+ References

No definition available.

+ Details

Name:	coop_LoansReceivableHeldforsaleReconciliationtoCashFlowTransferfromHeldforsaletoHeldForInvestmentorOtherAssets
Namespace Prefix:	coop_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Repurchase of Ginnie Mae Receivables

+ References

No definition available.

+ Details

Name:	coop_RepurchaseofGinnieMaeReceivables
Namespace Prefix:	coop_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, before valuation allowance, of financing receivable classified as held-for-sale.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477011/948-310-45-1

+ Details

Name:	us-gaap_LoansReceivableHeldForSaleAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ Details

Name:	us-gaap_LoansReceivableHeldForSaleNetReconciliationToCashFlowRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after allowance for credit loss, of addition to financing receivable held for sale that is not part of disposal group.

+ References

+ Details

Name:	us-gaap_LoansReceivableHeldForSaleReconciliationToCashFlowAdditionsToHeldForSale
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, after allowance for credit loss, of deduction to financing receivable held for sale that is not part of disposal group.

+ References

+ Details

Name:	us-gaap_LoansReceivableHeldForSaleReconciliationToCashFlowDeductionsFromHeldForSale
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration