Derivative Financial Instruments - Schedule of Interest Rate Swaps (Details) - USD ($) |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Interest rate swaps - Nelnet Bank intercompany deposits | ||
| Derivative [Line Items] | ||
| Notional amount | $ 195,000,000 | |
| Weighted-average fixed rate paid by the Company | 3.50% | |
| 2028 | ||
| Derivative [Line Items] | ||
| Notional amount | $ 40,000,000 | |
| Weighted-average fixed rate paid by the Company | 3.33% | |
| 2029 | ||
| Derivative [Line Items] | ||
| Notional amount | $ 25,000,000 | |
| Weighted-average fixed rate paid by the Company | 3.37% | |
| 2030 | ||
| Derivative [Line Items] | ||
| Notional amount | $ 50,000,000 | |
| Weighted-average fixed rate paid by the Company | 3.06% | |
| 2032 | ||
| Derivative [Line Items] | ||
| Notional amount | $ 25,000,000 | $ 25,000,000 |
| Weighted-average fixed rate paid by the Company | 4.03% | |
| 2033 | ||
| Derivative [Line Items] | ||
| Notional amount | $ 25,000,000 | |
| Weighted-average fixed rate paid by the Company | 3.90% | |
| 2035 | ||
| Derivative [Line Items] | ||
| Notional amount | $ 30,000,000 | $ 30,000,000 |
| Weighted-average fixed rate paid by the Company | 3.79% |