Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Total		$ 4,548,237	$ 4,135,130
Interest rate contracts [Member]
Derivative [Line Items]
Total		3,319,633	2,805,579
Interest Rate Futures and Forwards [Member]
Derivative [Line Items]
Total		830,442	501,635
Interest Rate Swap [Member]
Derivative [Line Items]
Total		2,367,130	2,142,183
Interest Rate Options Written [Member]
Derivative [Line Items]
Total		52,585	74,741
Interest Rate Options Purchased [Member]
Derivative [Line Items]
Total		69,476	87,020
Foreign exchange contracts [Member]
Derivative [Line Items]
Total		1,011,655	1,105,971
Foreign Exchange Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		908,523	965,301
Foreign Exchange Options Written [Member]
Derivative [Line Items]
Total		28,088	52,845
Foreign Exchange Options Purchased [Member]
Derivative [Line Items]
Total		29,921	53,260
Foreign Exchange Spot [Member]
Derivative [Line Items]
Total		45,123	34,565
Commodities, equities and precious metals contracts [Member]
Derivative [Line Items]
Total		120,441	99,682
Commodities, Equities and Precious Metals, Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		55,672	49,555
Commodities, Equities and Precious Metals Options Written [Member]
Derivative [Line Items]
Total		26,603	19,495
Commodities, Equities and Precious Metals Options Purchased [Member]
Derivative [Line Items]
Total		38,166	30,632
Credit contracts [Member]
Derivative [Line Items]
Total		95,914	123,714
Other Contract [Member]
Derivative [Line Items]
Total	[1]	$ 594	$ 184

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