XML 48 R38.htm IDEA: XBRL DOCUMENT
v3.25.2

Allowance for Loan Losses - Private Education Loan Portfolio Stratified by Key Credit Quality Indicators (Parenthetical) (Detail) | Jun. 30, 2025 | Jun. 30, 2024
--- | --- | ---
With Cosigner [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Total Private Education Loan Credit Quality Indicators, Excluding Refinance Loans, Percent | 66.00% | 66.00%

X
- Definition Loans and leases receivable gross carrying amount percent. + References No definition available. + Details
Name: | navi_LoansAndLeasesReceivableGrossCarryingAmountPercent
Namespace Prefix: | navi_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- 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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=navi_CosignerLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |