Mortgage Loans Held for Sale - Mortgage Loans Held for Sale (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans held for sale – UPB	$ 1,916	$ 924
Mark-to-market adjustment(1)	46	3
Total mortgage loans held for sale	1,962	927
UPB	47	42
Fair Value	37	36
Ginnie mae repurchased loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
UPB	$ 34	$ 35

Fair Value, Mortgage Loans Held for Sale non-accrual status

No definition available.

Name:	coop_FairValueMortgageLoansHeldforSalenonaccrualstatus
Namespace Prefix:	coop_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Loans Held-for-Sale, Mortgages, Fair Value Adjustment

+ References

No definition available.

+ Details

Name:	coop_LoansHeldForSaleMortgagesFairValueAdjustment
Namespace Prefix:	coop_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Loans Held-for-Sale, Mortgages, Unpaid Principal Balance

+ References

No definition available.

+ Details

Name:	coop_LoansHeldForSaleMortgagesUnpaidPrincipalBalance
Namespace Prefix:	coop_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Mortgage Loans Held for Sale, Nonaccrual Basis Unpaid Principal Balance

+ References

No definition available.

+ Details

Name:	coop_MortgageLoansHeldforSaleNonaccrualBasisUnpaidPrincipalBalance
Namespace Prefix:	coop_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481628/310-20-40-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-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

+ Details

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

- Definition

Amount, after valuation allowance, of financing receivable held for sale and not part of disposal group. Excludes loan covered under loss sharing agreement and loan classified as investment in debt security.

+ 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_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancialInstrumentAxis=coop_GinnieMaeRepurchasedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: