Loans and Accrued Interest Receivable and Allowance for Loan Losses - Schedule of Net Charge-offs as a Percentage of Average Loans (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Federally insured loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	0.16%	0.16%	0.16%	0.14%
Private education loans - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	0.46%	0.55%	0.54%	1.02%
Consumer loans and other financing receivables - Non-Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	8.78%	7.62%	8.86%	6.58%
Federally insured loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	0.07%	0.06%	0.07%	0.06%
Private education loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	0.87%	1.10%	1.00%	1.08%
Consumer and other loans - Nelnet Bank
Financing Receivable, Credit Ratio [Line Items]
Net charge-offs as a percentage of average loans	1.10%	1.71%	1.50%	1.49%