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Segment Reporting - Segment Result and Reconciliations to GAAP - Core Earnings Adjustments (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting [Abstract]
Other derivative accounting adjustments	$ 63	$ 42	$ (32)
Unrealized gains (losses) on derivative and hedging activities, net	$ 487	$ 115	$ (153)

X

- Definition

Other derivative accounting adjustments.

+ References

No definition available.

+ Details

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

X

- Definition

Unrealized gains (loss) on derivative and hedging activities, net.

+ References

No definition available.

+ Details

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

X

- Details

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