Consolidated Balance Sheets - Supplemental Information (Unaudited) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Short-term borrowings	$ 4,662	$ 5,870
Long-term borrowings	54,907	61,026
FFELP Loans [Member]
Loans, net	39,581	43,525
Private Education Loans [Member]
Loans, net	17,333	18,725
Assets and Liabilities of Consolidated Variable Interest Entities [Member]
Loans, net	55,682	60,672
Restricted cash	1,798	3,233
Other assets, net	1,615	1,356
Short-term borrowings	3,772	4,458
Long-term borrowings	49,849	55,598
Net assets of consolidated variable interest entities	5,474	5,205
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | FFELP Loans [Member]
Loans, net	39,493	43,465
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | Private Education Loans [Member]
Loans, net	$ 16,189	$ 17,207