XML 44 R31.htm IDEA: XBRL DOCUMENT
v3.19.2

Allowance for Loan Losses - Additional Information (Detail) $ in Billions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2019 USD ($) Loan | Dec. 31, 2018 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items] |  |
Percentage of loans granted forbearance that migrated to TDR classification | 68.00% | 65.00%
Payment default period for TDRs | 60 days past due |
Interest Rate Reduction [Member] |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |
TDR loans, Unpaid Principal Balance | $ | $ 2.0 | $ 1.8
Minimum [Member] |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |
Delinquency period (in days) | 212 days |
Private Education Loans [Member] |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |
Number of classes of loans | Loan | 2 |

X
- Definition Number of classes of loans. + References No definition available. + Details
Name: | navi_NumberOfClassesOfLoans
Namespace Prefix: | navi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payment default period for troubled debt restructurings. + References No definition available. + Details
Name: | navi_PaymentDefaultPeriodForTroubledDebtRestructurings
Namespace Prefix: | navi_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of loans granted forbearance that migrated to troubled debt restructuring classification. + References No definition available. + Details
Name: | navi_PercentageOfLoansGrantedForbearanceThatMigratedToTroubledDebtRestructuringClassification
Namespace Prefix: | navi_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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 No definition available. + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524 + Details
Name: | us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Threshold period past due for financing receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_ThresholdPeriodPastDueForWriteoffOfFinancingReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_LoanRestructuringModificationAxis=us-gaap_ContractualInterestRateReductionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=navi_PrivateEducationLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |