Loans In Repayment And Percentage Of Each Status [Abstract]

No definition available.

Name:	navi_LoansInRepaymentAndPercentageOfEachStatusAbstract
Namespace Prefix:	navi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-20

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-20

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-11B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph c
-Publisher SEC

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (1)
-Publisher SEC

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (3)
-Publisher SEC

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amortized cost, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

+ Details

Name:	us-gaap_FinancingReceivableBeforeAllowanceForCreditLossAndFee
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of financing receivable balance that is past due.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivablePercentPastDue1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-13

Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-29

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (1)
-Publisher SEC

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (2)
-Publisher SEC

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Regulation S-K (SK)
-Number 229
-Section 1404
-Paragraph a
-Publisher SEC

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 80
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-80

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-14

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_NotesReceivableGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(5)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

Name:	us-gaap_NotesReceivableNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Allowance for Loan Losses - Age Analysis of Past Due Loans Delinquencies (Detail) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2022
Loans in repayment and percentage of each status:
Loan allowance for losses	$ (687)	$ (857)	$ (832)	$ (744)	$ (920)	$ (1,022)
FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	33,134	41,051
Loan allowance for losses	(194)	(200)	(215)	(206)	(214)	(222)
Loans, net	32,940		37,925
Credit Concentration Risk [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	33,134	41,051	38,140
Loan allowance for losses	(194)	(200)	(215)
Loans, net	$ 32,940	$ 40,851	$ 37,925
Dimensions of concentration risk	100.00%	100.00%	100.00%
Credit Concentration Risk [Member] \| Financing Receivables, Current [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	86.50%	83.90%	86.10%
Credit Concentration Risk [Member] \| Financing Receivables, 31 to 60 Days Past Due [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Loans delinquent, percentage	3.90%	4.80%	3.90%
Credit Concentration Risk [Member] \| Financing Receivables, 61 to 90 Days Past Due [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Loans delinquent, percentage	2.60%	3.10%	2.50%
Credit Concentration Risk [Member] \| Financing Receivables, 90 Days Past Due [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Loans delinquent, percentage	7.00%	8.20%	7.50%
Credit Concentration Risk [Member] \| Financing Receivables, Loans In Repayment [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	79.70%	80.60%	79.80%
Credit Concentration Risk [Member] \| Financing Receivables, Delinquent Loans in Repayment [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	13.50%	16.10%	13.90%
Credit Concentration Risk [Member] \| Financing Receivables, Forbearance, Loans In Repayment [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	16.80%	16.00%	16.80%
School/Grace/Deferment [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	$ 1,403	$ 1,659	$ 1,557
Forbearance [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	5,320	6,316	6,147
Repayment [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	26,411	33,076	30,436
Repayment [Member] \| Credit Concentration Risk [Member] \| Financing Asset, Not Past Due [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	22,833	27,756	26,204
Repayment [Member] \| Credit Concentration Risk [Member] \| Financial Asset, 31 to 60 Days Past Due [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	1,041	1,596	1,193
Repayment [Member] \| Credit Concentration Risk [Member] \| Financial Asset, 61 to 90 Days Past Due [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	680	1,013	746
Repayment [Member] \| Credit Concentration Risk [Member] \| Financial Asset, 90 Days Past Due [Member] \| Accounts Receivable [Member] \| FFELP Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	1,857	2,711	2,293
Private Education Loans [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	16,731	18,389
Loan allowance for losses	(493)	(657)	(617)	$ (538)	$ (706)	$ (800)
Loans, net	16,238	17,732	16,902
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	16,731	18,389	17,519
Loan allowance for losses	(493)	(657)	(617)
Loans, net	$ 16,238	$ 17,732	$ 16,902
Dimensions of concentration risk	100.00%	100.00%	100.00%
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Financing Receivables, Current [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	94.80%	95.60%	94.90%
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Financing Receivables, 31 to 60 Days Past Due [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Loans delinquent, percentage	1.90%	1.60%	1.80%
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Financing Receivables, 61 to 90 Days Past Due [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Loans delinquent, percentage	1.10%	0.80%	1.00%
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Financing Receivables, 90 Days Past Due [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Loans delinquent, percentage	2.20%	2.00%	2.30%
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Financing Receivables, Loans In Repayment [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	96.20%	96.40%	95.90%
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Financing Receivables, Delinquent Loans in Repayment [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	5.20%	4.40%	5.10%
Private Education Loans [Member] \| Credit Concentration Risk [Member] \| Financing Receivables, Forbearance, Loans In Repayment [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Dimensions of concentration risk	1.80%	1.80%	2.10%
Private Education Loans [Member] \| School/Grace/Deferment [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	$ 350	$ 341	$ 360
Private Education Loans [Member] \| Forbearance [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	294	328	363
Private Education Loans [Member] \| Repayment [Member] \| Credit Concentration Risk [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross	16,087	17,720	16,796
Private Education Loans [Member] \| Repayment [Member] \| Credit Concentration Risk [Member] \| Financing Asset, Not Past Due [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross		16,942	15,935
Total Loans, gross	15,250
Private Education Loans [Member] \| Repayment [Member] \| Credit Concentration Risk [Member] \| Financial Asset, 31 to 60 Days Past Due [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross		276	308
Total Loans, gross	311
Private Education Loans [Member] \| Repayment [Member] \| Credit Concentration Risk [Member] \| Financial Asset, 61 to 90 Days Past Due [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross		151	173
Total Loans, gross	175
Private Education Loans [Member] \| Repayment [Member] \| Credit Concentration Risk [Member] \| Financial Asset, 90 Days Past Due [Member] \| Accounts Receivable [Member]
Loans in repayment and percentage of each status:
Total Loans, gross		$ 351	$ 380
Total Loans, gross	$ 351