v3.26.1
Borrowings - Company Borrowings (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Debt Instrument [Line Items]    
Short-Term $ 0 $ 498,415
Long-Term 5,844,116 5,362,494
Total 5,844,116 5,860,909
Unsecured borrowings    
Debt Instrument [Line Items]    
Short-Term 0 498,415
Long-Term 988,122 493,415
Total 988,122 991,830
Secured Borrowings    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 4,855,994 4,869,079
Total 4,855,994 4,869,079
Secured Borrowings | Private Education Loan term securitizations    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 4,855,994 4,869,079
Total 4,855,994 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 | Fixed-rate | Private Education Loan term securitizations    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 4,204,866 4,174,513
Total 4,204,866 4,174,513
Secured Borrowings | Variable-rate | Private Education Loan term securitizations    
Debt Instrument [Line Items]    
Short-Term 0 0
Long-Term 651,128 694,566
Total $ 651,128 $ 694,566