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Loans and Accrued Interest Receivable and Allowance for Loan Losses - Allowance for Loan Losses as a Percentage of the Ending Balance (Details)	Dec. 31, 2024	Dec. 31, 2023
Federally insured loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Allowance for loan losses as a percentage of the ending balance	0.59%	0.59%
Allowance for loan losses as a percentage of the risk sharing component, not covered by the federal guaranty	20.60%	21.80%
Private education loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Allowance for loan losses as a percentage of the ending balance	5.02%	5.68%
Consumer loans and other loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Allowance for loan losses as a percentage of the ending balance	11.13%	13.66%
Private education loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Allowance for loan losses as a percentage of the ending balance	2.09%	0.93%
Consumer and other loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Allowance for loan losses as a percentage of the ending balance	3.77%	7.40%

X

- Definition

Financing Receivable, Allowance for Credit Loss to Risk Sharing Component, Not Covered by the Federal Guaranty, Percent

+ References

No definition available.

+ Details

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- Definition

Percentage of allowance for credit loss to total financing receivable outstanding.

+ References

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

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- Definition

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-Number 229
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
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-Number 229
-Section 1405
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