Commitments, Contingencies and Guarantees - Additional Information (Detail)	1 Months Ended	3 Months Ended
	Jan. 31, 2022 USD ($) StateAttorneysGeneral Borrower	Dec. 31, 2021 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Loss Contingencies [Line Items]
Probable contingency loss liability			$ 105,000,000	$ 85,000,000	$ 73,000,000
Number of State Attorneys General under Agreement | StateAttorneysGeneral	40
Number of borrowers involved in cancellation of loan balance | Borrower	66,000
Aggregate outstanding balance of loans cancelled	$ 1,700,000,000
Expense on cancellation of loans	50,000,000
One-time payment	$ 145,000,000
Regulatory expenses		$ 205,000,000
Minimum [Member]
Loss Contingencies [Line Items]
Probable contingency loss liability			0
Maximum [Member]
Loss Contingencies [Line Items]
Probable contingency loss liability			250,000,000
SLM BankCo [Member] | Indemnification Matters [Member]
Loss Contingencies [Line Items]
Accrued liabilities related to indemnification matters			$ 0