Derivative Financial Instruments - Notional Value of Derivative Contracts (Detail) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Total		$ 5,609,194	$ 4,793,784
Interest rate contracts [Member]
Derivative [Line Items]
Total		4,197,649	3,593,216
Interest Rate Futures and Forwards [Member]
Derivative [Line Items]
Total		1,127,140	735,757
Interest Rate Swap [Member]
Derivative [Line Items]
Total		2,845,502	2,687,273
Interest Rate Options Written [Member]
Derivative [Line Items]
Total		109,413	77,144
Interest Rate Options Purchased [Member]
Derivative [Line Items]
Total		115,594	93,042
Foreign exchange contracts [Member]
Derivative [Line Items]
Total		1,192,357	996,092
Foreign Exchange Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		1,107,705	924,163
Foreign Exchange Options Written [Member]
Derivative [Line Items]
Total		25,363	25,911
Foreign Exchange Options Purchased [Member]
Derivative [Line Items]
Total		25,915	26,617
Foreign Exchange Spot [Member]
Derivative [Line Items]
Total		33,374	19,401
Commodities, equities and precious metals contracts [Member]
Derivative [Line Items]
Total		137,955	113,542
Commodities, Equities and Precious Metals, Swaps, Futures and Forwards [Member]
Derivative [Line Items]
Total		61,360	38,709
Commodities, Equities and Precious Metals Options Written [Member]
Derivative [Line Items]
Total		32,250	31,631
Commodities, Equities and Precious Metals Options Purchased [Member]
Derivative [Line Items]
Total		44,345	43,202
Credit contracts [Member]
Derivative [Line Items]
Total		80,558	90,290
Other Contract [Member]
Derivative [Line Items]
Total	[1]	$ 675	$ 644

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