Gain (loss) on loan disbursement amount.

No definition available.

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- Definition

Gain (loss) on loan disbursement amount including basis.

+ References

No definition available.

+ Details

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- Definition

Gain (loss) on loan, remaining disbursement amount.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Loan outstanding amount.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loan outstanding amount from trust.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loan receivable, disbursement amount.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Loan receivable, fair value option, pre-disbursement amount.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loan receivable originated amount.

+ References

No definition available.

+ Details

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Namespace Prefix:	navi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of legacy private education loan securitization trust.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of third party valuation specialist origination.

+ References

No definition available.

+ Details

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Namespace Prefix:	navi_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- 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
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Period Type:	duration

- Definition

Amount of expense reversal of allowance for credit loss on financing receivable transferred to held-for-sale classification.

+ References

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- Definition

The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes.

+ References

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Balance Type:	credit
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- Definition

Amount, before valuation allowance, of financing receivable classified as held-for-sale.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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Education Loans - Additional Information (Details) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended			9 Months Ended
	Oct. 01, 2026 USD ($)	Sep. 30, 2026 USD ($) Loan	Sep. 30, 2026 USD ($) $ / shares	Jun. 30, 2026 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2026 USD ($)	Sep. 30, 2025 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale		$ 2,400	$ 2,400			$ 2,400
Gains on sales of loans			162		$ 0	162	$ 0
In School Private Education Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivable originated amount			479
Loan receivable disbursement amount			$ 226
Percentage of third party valuation specialist origination \| $ / shares			$ 105
Gain (loss) on loan disbursement amount			$ 23
Gain (loss) on loan disbursement amount including basis			11
Gain (loss) on loan remaining disbursement amount			12
Loans held for sale		1,000	1,000			1,000
Allowance for loan loss						42
In School Private Education Loans [Member] \| Subsequent Event [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivable pre-disbursement amount	$ 253
Legacy Private Education Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale		2,339	2,339	$ 5,700		2,339
Allowance for loan loss						19
Loan outstanding amount				$ 600
Gains on sales of loans		$ 99				63
Loan outstanding amount from trust						150
Number of legacy private education loan securitization trust \| Loan		3
Provision for loan losses						29
Legacy Private Education Loans [Member] \| Consumer Lending [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale		$ 1,400	$ 1,400			$ 1,400