Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

No definition available.

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

+ Details

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

- Definition

Amount of debt for which creditor does not have general recourse to the debtor but rather has recourse only to the property used for collateral in the transaction or other specific property.

+ References

No definition available.

+ Details

Name:	us-gaap_NonRecourseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_ParticipatingInterestFinancingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_A20162HECMSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_A20163HECMSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_A201701HECMSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_A201702HECMSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_A201801HECMSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_A201802HECMSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_A201803HECMSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_OtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=nsm_LegacyAssetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=nsm_NonrecourseDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_PredecessorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Indebtedness - Non-Recourse Debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Non-recourse debt	$ 6,795
Participating Interest Financing
Debt Instrument [Line Items]
Non-recourse debt	5,607
Trust 2016-2
Debt Instrument [Line Items]
Non-recourse debt	0
Trust 2016-3
Debt Instrument [Line Items]
Non-recourse debt	0
Trust 2017-1
Debt Instrument [Line Items]
Non-recourse debt	0
Trust 2017-2
Debt Instrument [Line Items]
Non-recourse debt	231
Trust 2018-1
Debt Instrument [Line Items]
Non-recourse debt	284
Trust 2018-2
Debt Instrument [Line Items]
Non-recourse debt	250
Trust 2018-3
Debt Instrument [Line Items]
Non-recourse debt	326
Other
Debt Instrument [Line Items]
Non-recourse debt	6,727
Legacy Asset
Debt Instrument [Line Items]
Non-recourse debt	29
Non-recourse debt - legacy assets
Debt Instrument [Line Items]
Unamortized debt issuance costs, net of premium, and issuance discount	68
Non-recourse debt - legacy assets \| Participating Interest Financing
Debt Instrument [Line Items]
Securitized Amount	0
Non-recourse debt - legacy assets \| Trust 2016-2
Debt Instrument [Line Items]
Securitized Amount	0
Non-recourse debt - legacy assets \| Trust 2016-3
Debt Instrument [Line Items]
Securitized Amount	0
Non-recourse debt - legacy assets \| Trust 2017-1
Debt Instrument [Line Items]
Securitized Amount	0
Non-recourse debt - legacy assets \| Trust 2017-2
Debt Instrument [Line Items]
Securitized Amount	284
Non-recourse debt - legacy assets \| Trust 2018-1
Debt Instrument [Line Items]
Securitized Amount	308
Non-recourse debt - legacy assets \| Trust 2018-2
Debt Instrument [Line Items]
Securitized Amount	260
Non-recourse debt - legacy assets \| Trust 2018-3
Debt Instrument [Line Items]
Securitized Amount	350
Non-recourse debt - legacy assets \| Legacy Asset
Debt Instrument [Line Items]
Securitized Amount	$ 105
Predecessor
Debt Instrument [Line Items]
Non-recourse debt		$ 8,014
Predecessor \| Participating Interest Financing
Debt Instrument [Line Items]
Non-recourse debt		7,111
Predecessor \| Trust 2016-2
Debt Instrument [Line Items]
Non-recourse debt		94
Predecessor \| Trust 2016-3
Debt Instrument [Line Items]
Non-recourse debt		138
Predecessor \| Trust 2017-1
Debt Instrument [Line Items]
Non-recourse debt		213
Predecessor \| Trust 2017-2
Debt Instrument [Line Items]
Non-recourse debt		365
Predecessor \| Trust 2018-1
Debt Instrument [Line Items]
Non-recourse debt		0
Predecessor \| Trust 2018-2
Debt Instrument [Line Items]
Non-recourse debt		0
Predecessor \| Trust 2018-3
Debt Instrument [Line Items]
Non-recourse debt		0
Predecessor \| Other
Debt Instrument [Line Items]
Non-recourse debt		7,963
Predecessor \| Legacy Asset
Debt Instrument [Line Items]
Non-recourse debt		42
Predecessor \| Non-recourse debt - legacy assets
Debt Instrument [Line Items]
Unamortized debt issuance costs, net of premium, and issuance discount		$ 51