Consolidated Balance Sheets - Supplemental Information (Unaudited) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Short-term borrowings	$ 5,305	$ 4,226
Long-term borrowings	44,695	53,402
FFELP Loans [Member]
Loans, net	31,522	37,925
Private Education Loans [Member]
Loans, net	16,005	16,902
Assets and Liabilities of Consolidated Variable Interest Entities [Member]
Loans, net	46,062	53,591
Restricted cash	1,631	1,937
Other assets, net	1,336	1,744
Short-term borrowings	4,174	3,634
Long-term borrowings	39,916	48,169
Net assets of consolidated variable interest entities	4,939	5,469
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | FFELP Loans [Member]
Loans, net	31,322	37,832
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | Private Education Loans [Member]
Loans, net	$ 14,740	$ 15,759