Name:	onit_HMBSRelatedBorrowingsAdditionalProceedsFromSecuritizationOfHECMLoansAndTails
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Change in fair value related to home equity conversion mortgage-backed securities related borrowings accounted for as a financing.

No definition available.

Name:	onit_HMBSRelatedBorrowingsChangeInFairValue
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Principal repayment in connection with home equity conversion mortgage-backed securities related borrowings accounted for as a financing.

No definition available.

Name:	onit_HMBSRelatedBorrowingsRepayments
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amounts related to securitization of home equity conversion mortgage-backed securities related borrowings accounted for as a financing.

No definition available.

Name:	onit_HMBSRelatedBorrowingsSecuritization
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

This represents the amount of liability which is a resultant of reverse mortgage loans sold into the secondary with servicing rights retained. As the transfer of these loans do not meet the definition of participating interest because of the servicing requirement that requires the issuer to absorb some level of risk, these transfers are accounted for as financing.

No definition available.

Name:	onit_HomeEquityConversionMortgageBackedSecuritiesRelatedBorrowingsAtFairValue
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Loans held for investment, reverse mortgages.

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgages
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Change in fair value of loans held for investment, reverse mortgages during the period.

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgagesFairValueChanges
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of loans held for investment, reverse mortgages transferred to loans held for sale, fair value during the period.

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgagesLoansHeldForSaleAtFairValue
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of loans held for investment, reverse mortgages originated during the period.

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgagesOriginations
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Loans Held For Investment, Reverse Mortgages, Other

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgagesOther
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of loans held for investment, reverse mortgages transferred to real estate owned during the period.

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgagesRealEstateOwned
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of loans held for investment, reverse mortgages transferred to receivables during the period.

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgagesReceivablesNet
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Principal payments received on loans held for investment during the period.

No definition available.

Name:	onit_LoansHeldForInvestmentReverseMortgagesRepayments
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale Reverse Mortgages

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgages
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Loans Held For Sale, Reverse Mortgages, Fair Value Adjustment

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesFairValueAdjustment
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Loans Held For Sale, Reverse Mortgages, Fair Value Changes

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesFairValueChanges
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Originations

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesOriginations
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Repayments

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesRepayments
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Repayments Of Loans Previously Held For Investment

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesRepaymentsOfLoansPreviouslyHeldForInvestment
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Transfer To Other

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesTransferToOther
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Transfers To Loans Held For Sale, At Fair Value

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesTransfersToLoansHeldForSaleAtFairValue
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Transfers To Real Estate Owned

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesTransfersToRealEstateOwned
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Transfers To Receivables, net

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesTransfersToReceivablesNet
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans Held For Sale, Reverse Mortgages, Unpaid Principal

No definition available.

Name:	onit_LoansHeldForSaleReverseMortgagesUnpaidPrincipal
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Loans Receivable, Fair Value Disclosure, Pending Pooling

No definition available.

Name:	onit_LoansReceivableFairValueDisclosurePendingPooling
Namespace Prefix:	onit_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.