v3.26.3
Borrowings - Company Borrowings (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Debt Instrument [Line Items]    
Short-Term $ 898,729 $ 498,415
Long-Term 5,535,923 5,362,494
Total 6,434,652 5,860,909
Unsecured borrowings    
Debt Instrument [Line Items]    
Short-Term 0 498,415
Long-Term 988,466 493,415
Total 988,466 991,830
Secured borrowings    
Debt Instrument [Line Items]    
Short-Term 898,729 0
Long-Term 4,547,457 4,869,079
Total 5,446,186 4,869,079
Secured borrowings | Private Education Loan term securitizations    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 4,547,457 4,869,079
Total 4,547,457 4,869,079
Secured borrowings | Secured Borrowing Facility    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 0 0
Total 0 0
Secured borrowings | Secured Warehouse Facility    
Debt Instrument [Line Items]    
Short-Term 898,729 0
Long-Term 0 0
Total 898,729 0
Secured borrowings | Fixed-rate | Private Education Loan term securitizations    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 3,947,591 4,174,513
Total 3,947,591 4,174,513
Secured borrowings | Variable-rate | Private Education Loan term securitizations    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 599,866 694,566
Total $ 599,866 $ 694,566