Borrowings - Company's Borrowings (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Long-term debt	$ 53,402	$ 61,026
Short-term Debt	4,226	5,870
FFELP Loan Securitizations ABS Repurchase Facilities [Member]
Debt Instrument [Line Items]
Debt tranches default principal amount	1,600
Total Before Hedge Accounting Adjustments [Member]
Debt Instrument [Line Items]
Long-term debt	53,680	61,516
Short-term Debt	4,235	5,880
Total Before Hedge Accounting Adjustments [Member] | FFELP Loan Securitizations ABS Repurchase Facilities [Member]
Debt Instrument [Line Items]
Long-term debt	122	0
Short-term Debt	59	76
Total Before Hedge Accounting Adjustments [Member] | Non-U.S. Doller Denominated Debt [Member]
Debt Instrument [Line Items]
Long-term debt	1,600	1,800
Total Before Hedge Accounting Adjustments [Member] | Private Education Loan Asset-backed Securitization Repurchase Facilities [Member]
Debt Instrument [Line Items]
Short-term Debt	435	725
Total Before Hedge Accounting Adjustments [Member] | Long-Term Floating Rate Debt [Member]
Debt Instrument [Line Items]
Long-term debt	38,200	44,900
Total Before Hedge Accounting Adjustments [Member] | Long-Term Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Long-term debt	15,500	16,600
Total Before Hedge Accounting Adjustments [Member] | Short Term Senior Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt principal amount	506	1,300
Total Before Hedge Accounting Adjustments [Member] | Long Term Senior Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt principal amount	$ 5,400	$ 5,700