Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Total		$ 2,021,133	$ 4,807,851
Interest rate contracts [Member]
Derivative [Line Items]
Total		509,403	3,051,548
Interest Rate Futures and Forwards [Member]
Derivative [Line Items]
Total		37,098	597,980
Interest Rate Swap [Member]
Derivative [Line Items]
Total		406,609	2,130,442
Interest Rate Options Written [Member]
Derivative [Line Items]
Total		33,269	158,861
Interest Rate Options Purchased [Member]
Derivative [Line Items]
Total		32,427	164,265
Foreign exchange contracts [Member]
Derivative [Line Items]
Total		1,359,284	1,520,980
Foreign Exchange Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		1,195,449	1,362,959
Foreign Exchange Options Written [Member]
Derivative [Line Items]
Total		53,200	44,876
Foreign Exchange Options Purchased [Member]
Derivative [Line Items]
Total		53,595	46,085
Foreign Exchange Spot [Member]
Derivative [Line Items]
Total		57,040	67,060
Commodities, equities and precious metals contracts [Member]
Derivative [Line Items]
Total		98,619	144,230
Commodities, Equities and Precious Metals, Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		54,458	55,678
Commodities, Equities and Precious Metals Options Written [Member]
Derivative [Line Items]
Total		17,078	39,035
Commodities, Equities and Precious Metals Options Purchased [Member]
Derivative [Line Items]
Total		27,083	49,517
Credit contracts [Member]
Derivative [Line Items]
Total		52,611	90,049
Other Contracts [Member]
Derivative [Line Items]
Total	[1]	$ 1,216	$ 1,044

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