XML 43 R31.htm IDEA: XBRL DOCUMENT v3.5.0.2

Allowance for Loan Losses - Allowance for Credit Losses and Recorded Investments in Loans (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net adjustment resulting from the change in the charge-off rate	$ 330		$ 330
Private Education Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portion of loan amount charged off at default	79.00%	73.00%
Net adjustment resulting from the change in the charge-off rate	$ 330		$ 330

X

- Definition

Net adjustment from change in charge off rate.

+ References

No definition available.

+ Details

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

X

- Definition

Portion of loan amount charged off at default.

+ References

No definition available.

+ Details

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

X

- Details

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