Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Total		$ 5,512,901	$ 5,556,668
Interest rate contracts [Member]
Derivative [Line Items]
Total		3,959,386	4,203,667
Interest Rate Futures and Forwards [Member]
Derivative [Line Items]
Total		750,139	787,049
Interest Rate Swap [Member]
Derivative [Line Items]
Total		2,993,980	3,203,048
Interest Rate Options Written [Member]
Derivative [Line Items]
Total		104,512	106,009
Interest Rate Options Purchased [Member]
Derivative [Line Items]
Total		110,755	107,561
Foreign exchange contracts [Member]
Derivative [Line Items]
Total		1,309,169	1,144,808
Foreign Exchange Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		1,177,668	1,052,088
Foreign Exchange Options Written [Member]
Derivative [Line Items]
Total		43,821	30,567
Foreign Exchange Options Purchased [Member]
Derivative [Line Items]
Total		45,005	31,069
Foreign Exchange Spot [Member]
Derivative [Line Items]
Total		42,675	31,084
Commodities, equities and precious metals contracts [Member]
Derivative [Line Items]
Total		126,249	110,159
Commodities, Equities and Precious Metals, Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		43,310	41,328
Commodities, Equities and Precious Metals Options Written [Member]
Derivative [Line Items]
Total		35,600	28,595
Commodities, Equities and Precious Metals Options Purchased [Member]
Derivative [Line Items]
Total		47,339	40,236
Credit contracts [Member]
Derivative [Line Items]
Total		117,225	97,298
Other Contracts [Member]
Derivative [Line Items]
Total	[1]	$ 872	$ 736

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