| Document | Feb. 25, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 25, 2021 |
| Entity Registrant Name | NELNET, INC |
| Entity Central Index Key | 0001258602 |
| Entity Incorporation, State or Country Code | NE |
| Entity File Number | 001-31924 |
| Entity Tax Identification Number | 84-0748903 |
| Entity Address, Address Line One | 121 South 13th Street, Suite 100 |
| Entity Address, City or Town | Lincoln, |
| Entity Address, State or Province | NE |
| Entity Address, Postal Zip Code | 68508 |
| City Area Code | 402 |
| Local Phone Number | 458-2370 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A Common Stock, Par Value $0.01 per Share |
| Trading Symbol | NNI |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
