Mortgage Loans Held for Sale - Reconciliation to Cash Flow (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2022	Sep. 30, 2021
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance - beginning of period	$ 4,381	$ 5,720
Loans sold	(30,648)	(73,822)
Mortgage loans originated and purchased, net of fees	25,120	67,507
Repurchase of loans out of Ginnie Mae securitizations	2,904	8,530
Net change in unrealized (loss) gain on retained loans held for sale	(177)	1
Net transfers of mortgage loans held for sale(1)	1	3
Balance - end of period	$ 1,581	$ 7,939

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/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124265262&loc=d3e48678-111004

+ 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 bad debt, of additions to loan receivables held-for-sale that are not part of a disposal group.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

+ Details

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

- Definition

Amount, after allowance for bad debt, of deductions to loan receivables held-for-sale that are not part of a disposal group.

+ References

+ Details

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