v3.25.2
Investments and Notes Receivable - Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value (Details)
Jun. 30, 2025
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 (1,846,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (20,850,000)
Total, unrealized loss (22,696,000)
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 275,392,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 259,190,000
Total, fair value 534,582,000
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 (389,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (19,471,000)
Total, unrealized loss (19,860,000)
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 33,512,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 229,196,000
Total, fair value 262,708,000
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 (245,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (2,811,000)
Total, unrealized loss (3,056,000)
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 9,992,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 45,914,000
Total, fair value 55,906,000
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 (129,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (321,000)
Total, unrealized loss (450,000)
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 21,535,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 8,014,000
Total, fair value 29,549,000
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 0
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (16,339,000)
Total, unrealized loss (16,339,000)
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 0
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 175,268,000
Total, fair value 175,268,000
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 (15,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss 0
Total, unrealized loss (15,000)
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 1,985,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 0
Total, fair value 1,985,000
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 (1,457,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (1,379,000)
Total, unrealized loss (2,836,000)
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 241,880,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 29,994,000
Total, fair value 271,874,000
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 (481,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (233,000)
Total, unrealized loss (714,000)
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 58,186,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 16,216,000
Total, fair value 74,402,000
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 0
Total, unrealized loss (1,000)
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 14,208,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 0
Total, fair value 14,208,000
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 (975,000)
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, unrealized loss (1,146,000)
Total, unrealized loss (2,121,000)
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 169,486,000
Available-for-sale asset-backed securities, unrealized loss position 12 months or more, fair value 13,778,000
Total, fair value $ 183,264,000