v3.26.1
Investments and Notes Receivable - Schedule of Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value (Details)
Jun. 30, 2026
USD ($)
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]  
Asset -backed securities unrealized loss position not due to credit loss $ 0
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (3,067,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (14,927,000)
Total, unrealized loss (17,994,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 594,201,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 260,647,000
Total, fair value 854,848,000
Total Non-Nelnet Bank  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (466,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (12,670,000)
Total, unrealized loss (13,136,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 121,083,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 153,775,000
Total, fair value 274,858,000
FFELP loan  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (10,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (136,000)
Total, unrealized loss (146,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 7,921,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 2,408,000
Total, fair value 10,329,000
FFELP loan and other debt securities - restricted  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (379,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (283,000)
Total, unrealized loss (662,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 95,553,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 16,719,000
Total, fair value 112,272,000
Private education loan  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (7,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (12,251,000)
Total, unrealized loss (12,258,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 208,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 134,648,000
Total, fair value 134,856,000
Other debt securities  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (70,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss 0
Total, unrealized loss (70,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 17,401,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 0
Total, fair value 17,401,000
Total Nelnet Bank  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (2,601,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (2,257,000)
Total, unrealized loss (4,858,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 473,118,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 106,872,000
Total, fair value 579,990,000
FFELP loan  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (154,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (624,000)
Total, unrealized loss (778,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 38,238,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 53,641,000
Total, fair value 91,879,000
Private education loan  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (1,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (34,000)
Total, unrealized loss (35,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 149,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 11,536,000
Total, fair value 11,685,000
Other debt securities  
Debt Securities, Available-for-Sale, Unrealized Loss Position [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, unrealized loss (2,446,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (1,599,000)
Total, unrealized loss (4,045,000)
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]  
Available-for-sale asset-backed securities, unrealized loss position less than 12 months, fair value 434,731,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 41,695,000
Total, fair value $ 476,426,000