v3.26.1
Loans and Accrued Interest Receivable and Allowance for Loan Losses - Schedule of Allowance for Loan Losses as a Percentage of the Ending Balance (Details)
Jun. 30, 2026
Dec. 31, 2025
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% 0.57%
Allowance for loan losses as a percentage of the risk sharing component, not covered by the federal guaranty 20.10% 19.30%
Private education loans - Non-Nelnet Bank    
Financing Receivable, Credit Ratio [Line Items]    
Allowance for loan losses as a percentage of the ending balance 5.08% 4.95%
Consumer loans and other financing receivables - Non-Nelnet Bank    
Financing Receivable, Credit Ratio [Line Items]    
Allowance for loan losses as a percentage of the ending balance 7.60% 5.11%
Federally insured loans - Nelnet Bank    
Financing Receivable, Credit Ratio [Line Items]    
Allowance for loan losses as a percentage of the ending balance 0.35% 0.39%
Allowance for loan losses as a percentage of the risk sharing component, not covered by the federal guaranty 17.10% 17.30%
Private education loans - Nelnet Bank    
Financing Receivable, Credit Ratio [Line Items]    
Allowance for loan losses as a percentage of the ending balance 2.42% 2.49%
Consumer and other loans - Nelnet Bank    
Financing Receivable, Credit Ratio [Line Items]    
Allowance for loan losses as a percentage of the ending balance 4.84% 4.55%