Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Total		$ 1,751,830	$ 2,021,133
Interest rate contracts [Member]
Derivative [Line Items]
Total		366,868	509,403
Interest Rate Futures and Forwards [Member]
Derivative [Line Items]
Total		24,317	37,098
Interest Rate Swap [Member]
Derivative [Line Items]
Total		299,206	406,609
Interest Rate Options Written [Member]
Derivative [Line Items]
Total		20,766	33,269
Interest Rate Options Purchased [Member]
Derivative [Line Items]
Total		22,579	32,427
Foreign exchange contracts [Member]
Derivative [Line Items]
Total		1,247,516	1,359,284
Foreign Exchange Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		1,132,775	1,195,449
Foreign Exchange Options Written [Member]
Derivative [Line Items]
Total		36,859	53,200
Foreign Exchange Options Purchased [Member]
Derivative [Line Items]
Total		37,250	53,595
Foreign Exchange Spot [Member]
Derivative [Line Items]
Total		40,632	57,040
Commodities, equities and precious metals contracts [Member]
Derivative [Line Items]
Total		92,882	98,619
Commodities, Equities and Precious Metals, Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		62,759	54,458
Commodities, Equities and Precious Metals Options Written [Member]
Derivative [Line Items]
Total		10,340	17,078
Commodities, Equities and Precious Metals Options Purchased [Member]
Derivative [Line Items]
Total		19,783	27,083
Credit contracts [Member]
Derivative [Line Items]
Total		43,387	52,611
Other Contracts [Member]
Derivative [Line Items]
Total	[1]	$ 1,177	$ 1,216

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