Derivative Positions (Additional Information) (Detail) - USD ($) shares in Millions, $ in Millions	1 Months Ended
	May 31, 2009	Dec. 31, 2016	Dec. 31, 2015
Derivative Asset, Notional Amount		$ 133,395	$ 123,025
Derivative Liability, Notional Amount		153,160	123,514
Credit Risk Contract [Member]
Derivative Asset, Notional Amount		5	6
Derivative Liability, Notional Amount		13	9
Derivative Financial Instruments, Liabilities [Member] | Visa Interest [Member]
Number Of Shares Sold To Selected Financial Institutions	3.2
Visa Interest [Member] | Other Contract [Member]
Derivative Liability, Notional Amount		49	49
Interest rate futures [Member] | Mortgage Servicing Rights [Member]
Derivative Liability, Notional Amount		6,700	9,100
Interest rate futures [Member] | Loans Held For Sale [Member]
Derivative Asset, Notional Amount		720	518
Interest rate futures [Member] | Other Trading [Member]
Derivative Asset, Notional Amount		12,300	12,600
Equity futures [Member] | Equity Contract [Member]
Derivative Asset, Notional Amount		$ 629	$ 329