Name:	navi_EmployeeBenefitPlanDefinedContributionPlanHoursOfServiceRequirement
Namespace Prefix:	navi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Percentage of employer matching contribution for the first five percent of eligible participant compensation to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	navi_EmployeeBenefitPlanEmployerMatchingContributionToFirstFivePercentOfParticipantsCompensation
Namespace Prefix:	navi_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of eligible compensation increase in contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	navi_EmployeeBenefitPlanIncreaseInAutomaticDeferralRateEachYear
Namespace Prefix:	navi_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	duration

Maximum number of loans outstanding of participants.

No definition available.

Name:	navi_EmployeeBenefitPlanMaximumNumberOfLoansOutstanding
Namespace Prefix:	navi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Percentage of participant's eligible for 100% of employer matching contribution towards participant's compensation to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	navi_EmployeeBenefitPlanMaximumPercentageOfParticipantsEligibleForOneHundredPercentageOfEmployerMatchingContribution
Namespace Prefix:	navi_
Data Type:	dtr:percentItemType
Balance Type:	na
Period Type:	duration

Vesting case of normal retirement of death or disability (employee benefit plan (EBP)).

No definition available.

Name:	navi_EmployeeBenefitPlanNormalRetirement
Namespace Prefix:	navi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Period of repayment of loan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	navi_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingTerm
Namespace Prefix:	navi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Period of repayment of loan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	navi_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMinimumBorrowingTerm
Namespace Prefix:	navi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Period of repayment of loan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	navi_EmployeeBenefitPlanNoteReceivableFromParticipantPrincipalResidenceMaximumBorrowingTerm
Namespace Prefix:	navi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Number of employees transferred under employee benefit plan during the year.

No definition available.

Name:	navi_EmployeeBenefitPlanNumberOfEmployeesTransferred
Namespace Prefix:	navi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Partial repayment amount for loans of participants.

No definition available.

Name:	navi_EmployeeBenefitPlanPartialLoanRepayment
Namespace Prefix:	navi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Employee age limit to participate in the employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	navi_EmployeeBenefitPlanParticipantAgeLimitToParticipateInPlan
Namespace Prefix:	navi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Period of service of participants to be eligible for employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

No definition available.

Name:	navi_EmployeeBenefitPlanServicePeriodOfParticipantsToBeEligibleForMatchingContributionFromEmployer
Namespace Prefix:	navi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Minimum vesting period of service required from participants for matching contribution and Related earnings from employer.

No definition available.

Name:	navi_EmployeeBenefitPlanVestingPeriodOfServiceRequiredFromParticipantsForMatchingContributionAndRelatedEarningsFromEmployer
Namespace Prefix:	navi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Threshold percentage for investment applied to benchmark used for identifying concentration risk of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Name:	us-gaap-ebp_EbpRiskAndUncertaintyConcentrationOfInvestmentBenchmarkThresholdPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Indicates (true false) whether description of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) is published and made available.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Name:	us-gaap-ebp_EmployeeBenefitPlanDescriptionAvailable
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-SubTopic 205
-Topic 962
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Name:	us-gaap-ebp_EmployeeBenefitPlanDescriptionOfPlanLineItems
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Percentage of participant compensation eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Amount of plan asset, in forfeited nonvested account, no longer allocated to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from employer contribution.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (j)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(5)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForEmployerContribution
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

Name:	us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingAmount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow to total participant account balance.

Name:	us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingToTotalAccountPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanParticipantContributionAutomaticDeferralRate
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of maximum pretax annual compensation that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), is permitted to contribute to total pretax annual compensation.

Name:	us-gaap-ebp_EmployeeBenefitPlanParticipantContributionPretaxMaximumAnnualCompensationToTotalCompensationPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Interest rate on participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(D)
-Publisher DOL-EBSA