Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Total		$ 1,606,786	$ 2,021,133
Interest rate contracts [Member]
Derivative [Line Items]
Total		375,427	509,403
Interest Rate Futures and Forwards [Member]
Derivative [Line Items]
Total		53,008	37,098
Interest Rate Swap [Member]
Derivative [Line Items]
Total		298,670	406,609
Interest Rate Options Written [Member]
Derivative [Line Items]
Total		11,924	33,269
Interest Rate Options Purchased [Member]
Derivative [Line Items]
Total		11,825	32,427
Foreign exchange contracts [Member]
Derivative [Line Items]
Total		1,144,323	1,359,284
Foreign Exchange Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		1,011,881	1,195,449
Foreign Exchange Options Written [Member]
Derivative [Line Items]
Total		34,689	53,200
Foreign Exchange Options Purchased [Member]
Derivative [Line Items]
Total		34,772	53,595
Foreign Exchange Spot [Member]
Derivative [Line Items]
Total		62,981	57,040
Commodities, equities and precious metals contracts [Member]
Derivative [Line Items]
Total		78,333	98,619
Commodities, Equities and Precious Metals, Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		64,012	54,458
Commodities, Equities and Precious Metals Options Written [Member]
Derivative [Line Items]
Total		2,708	17,078
Commodities, Equities and Precious Metals Options Purchased [Member]
Derivative [Line Items]
Total		11,613	27,083
Credit contracts [Member]
Derivative [Line Items]
Total		7,465	52,611
Other Contracts [Member]
Derivative [Line Items]
Total	[1]	$ 1,238	$ 1,216

[1] Consists of swap agreements entered into in conjunction with the sales of Visa Class B Shares.