Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Total		$ 5,617,003	$ 5,556,668
Interest rate contracts [Member]
Derivative [Line Items]
Total		3,783,269	4,203,667
Interest Rate Futures and Forwards [Member]
Derivative [Line Items]
Total		729,684	787,049
Interest Rate Swap [Member]
Derivative [Line Items]
Total		2,855,855	3,203,048
Interest Rate Options Written [Member]
Derivative [Line Items]
Total		94,535	106,009
Interest Rate Options Purchased [Member]
Derivative [Line Items]
Total		103,195	107,561
Foreign exchange contracts [Member]
Derivative [Line Items]
Total		1,578,400	1,144,808
Foreign Exchange Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		1,417,913	1,052,088
Foreign Exchange Options Written [Member]
Derivative [Line Items]
Total		50,475	30,567
Foreign Exchange Options Purchased [Member]
Derivative [Line Items]
Total		51,493	31,069
Foreign Exchange Spot [Member]
Derivative [Line Items]
Total		58,519	31,084
Commodities, equities and precious metals contracts [Member]
Derivative [Line Items]
Total		134,857	110,159
Commodities, Equities and Precious Metals, Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		47,115	41,328
Commodities, Equities and Precious Metals Options Written [Member]
Derivative [Line Items]
Total		38,436	28,595
Commodities, Equities and Precious Metals Options Purchased [Member]
Derivative [Line Items]
Total		49,306	40,236
Credit contracts [Member]
Derivative [Line Items]
Total		119,521	97,298
Other Contracts [Member]
Derivative [Line Items]
Total	[1]	$ 956	$ 736

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