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Loans and Accrued Interest Receivable and Allowance for Loan Losses - Net Charge-offs as a Percentage of Average Loans (Details)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Federally insured loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	0.18%	0.15%	0.15%
Private education loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	1.70%	0.99%	1.18%
Consumer loans and other loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	7.58%	5.67%	2.05%
Federally insured loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	0.00%	0.02%	0.01%
Private education loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	0.60%	0.34%	0.10%
Consumer and other loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	6.69%	2.64%	0.00%

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- 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
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (1)
-Publisher SEC

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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-Subparagraph (3)
-Publisher SEC

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

Percentage of writeoff after recovery to average financing receivables outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Number 229
-Section 1405
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