Commitments, Contingent Liabilities and Guarantees - Visa Funding and Bancorp Cash Payments (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2019	Jun. 30, 2018	Sep. 30, 2014	Sep. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2008
Visa Funding Amount
Loss Contingencies
Escrow Deposit	$ 1,500	$ 150	$ 500	$ 350	$ 600	$ 250	$ 300	$ 600	$ 450	$ 150	$ 1,565	$ 400	$ 800	$ 500	$ 3,000
Bancorp Cash Payment Amount
Loss Contingencies
Cash Payment Amount	$ 65	$ 6	$ 21	$ 15	$ 25	$ 11	$ 12	$ 26	$ 18	$ 6	$ 75	$ 19	$ 35	$ 20