Derivatives and Hedging Activities - Gain (Loss) from Interest Rate Hedges and Related Hedged Borrowings and Deposits (Detail) - Interest Rate Contract [Member] - Fair Value Hedging [Member] - Derivative Contracts Accounted for as Hedges [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ (984)	$ 1,277	$ 1,865	$ (246)
Gain (Loss) Recognized On Hedged Borrowings and Deposits	823	(1,363)	(2,169)	(273)
Derivative, Net Hedge Ineffectiveness Gain (Loss)	$ (161)	$ (86)	$ (304)	$ (519)