v3.26.1
Borrowings - Financing VIEs (Detail) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Securities Financing Transaction [Line Items]    
Short-term borrowings $ 4,214 $ 5,073
Long-term borrowings 40,123 40,633
Total 44,337 45,706
Total assets 47,297 48,681
Total Before Hedge Accounting Adjustments [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 4,225 5,074
Long-term borrowings 40,208 40,672
Total 44,433 45,746
Hedge Accounting Adjustments [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings (11) (1)
Long-term borrowings (85) (39)
Total (96) (40)
Assets and Liabilities of Consolidated Variable Interest Entities [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 3,319 4,389
Long-term borrowings 35,550 35,835
Total 38,869 40,224
Loans 41,154 42,190
Cash 1,367 1,466
Other assets 1,252 1,300
Total assets 43,773 44,956
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | FFELP Loan Securitizations [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 0 109
Long-term borrowings 23,670 25,302
Total 23,670 25,411
Loans 24,309 25,942
Cash 784 950
Other assets 1,052 1,096
Total assets 26,145 27,988
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | Private Education Loan Securitizations [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 408 469
Long-term borrowings 10,847 10,250
Total 11,255 10,719
Loans 12,655 11,960
Cash 415 364
Other assets 154 127
Total assets 13,224 12,451
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | FFELP Loan ABCP Facilities [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 1,752 1,869
Long-term borrowings 499 299
Total 2,251 2,168
Loans 2,223 2,115
Cash 70 84
Other assets 114 108
Total assets 2,407 2,307
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | Private Education Loan ABCP Facilities [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 1,159 1,942
Long-term borrowings 574 0
Total 1,733 1,942
Loans 1,967 2,173
Cash 98 68
Other assets 23 44
Total assets 2,088 2,285
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | Total Before Hedge Accounting Adjustments [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 3,319 4,389
Long-term borrowings 35,590 35,851
Total 38,909 40,240
Loans 41,154 42,190
Cash 1,367 1,466
Other assets 1,343 1,375
Total assets 43,864 45,031
Assets and Liabilities of Consolidated Variable Interest Entities [Member] | Hedge Accounting Adjustments [Member]    
Securities Financing Transaction [Line Items]    
Short-term borrowings 0 0
Long-term borrowings (40) (16)
Total (40) (16)
Loans 0 0
Cash 0 0
Other assets (91) (75)
Total assets $ (91) $ (75)