Education Loans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounts Notes And Loans Receivable [Line Items]
Loans, net	$ 54,827	$ 62,250
Percentage of education loan portfolio in repayment	85.00%	84.00%
FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, net	$ 37,925	$ 43,525
After October 1 1993 and before July 1 2006 [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage reimbursement on all qualifying default claims period	98.00%
On or After July 1 2006 [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Percentage reimbursement on all qualifying default claims period	97.00%
Weighted Average [Member]
Accounts Notes And Loans Receivable [Line Items]
Estimated weighted average life of education loans	5 years	6 years
Stafford Loans [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, net	$ 13,564	$ 15,691
Stafford Loans [Member] | Minimum [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Repayment term	5 years
Stafford Loans [Member] | Maximum [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Repayment term	10 years
Consolidation Loans [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, net	$ 24,361	27,834
Consolidation Loans [Member] | Minimum [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Repayment term	12 years
Consolidation Loans [Member] | Maximum [Member] | FFELP Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Repayment term	30 years
Private Education Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, net	$ 16,902	$ 18,725
Private Education Loans [Member] | Minimum [Member]
Accounts Notes And Loans Receivable [Line Items]
Repayment term	10 years
Private Education Loans [Member] | Maximum [Member]
Accounts Notes And Loans Receivable [Line Items]
Repayment term	15 years
In School Loans [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans, net	$ 641