Fair Value Option - Components of Gain (Loss) on Instruments at Fair Value and Related Derivatives (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Mark-to-market on the related derivatives		$ 171	$ (308)	$ 336	$ 80
Gain (loss) on instruments designated at fair value and related derivatives		(38)	56	178	141
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	(202)	342	(353)	(28)
Credit risk component, total	[2],[3]	(36)	(22)	154	67
Total mark-to-market on financial instruments designated at fair value		(238)	320	(199)	39
Mark-to-market on the related derivatives		184	(281)	345	68
Net realized gain on the related long-term debt derivatives		16	17	32	34
Gain (loss) on instruments designated at fair value and related derivatives		(38)	56	178	141
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Loans [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	0	0	0	0
Credit risk component, assets	[2],[3]	3	2	0	(8)
Total mark-to-market on financial instruments designated at fair value		3	2	0	(8)
Mark-to-market on the related derivatives		0	0	0	0
Net realized gain on the related long-term debt derivatives		0	0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		3	2	0	(8)
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Securities purchased under resale agreements [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	0	0	5	0
Credit risk component, assets	[2],[3]	0	0	0	0
Total mark-to-market on financial instruments designated at fair value		0	0	5	0
Mark-to-market on the related derivatives		0	0	0	0
Net realized gain on the related long-term debt derivatives		0	0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		0	0	5	0
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Securities sold under repurchase agreements [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	(4)	(2)	1	(2)
Credit risk component, assets	[2],[3]	0	0	0	0
Total mark-to-market on financial instruments designated at fair value		(4)	(2)	1	(2)
Mark-to-market on the related derivatives		0	0	0	0
Net realized gain on the related long-term debt derivatives		0	0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		(4)	(2)	1	(2)
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Long-term debt [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	(70)	132	(197)	50
Credit risk component, liabilities	[2],[3]	(41)	48	108	118
Total mark-to-market on financial instruments designated at fair value		(111)	180	(89)	168
Mark-to-market on the related derivatives		67	(127)	194	(57)
Net realized gain on the related long-term debt derivatives		16	17	32	34
Gain (loss) on instruments designated at fair value and related derivatives		(28)	70	137	145
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Hybrid Instrument [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	[1]	(128)	212	(162)	(76)
Credit risk component, liabilities	[2],[3]	2	(72)	46	(43)
Total mark-to-market on financial instruments designated at fair value		(126)	140	(116)	(119)
Mark-to-market on the related derivatives		117	(154)	151	125
Net realized gain on the related long-term debt derivatives		0	0	0	0
Gain (loss) on instruments designated at fair value and related derivatives		$ (9)	$ (14)	$ 35	$ 6

[1] As it relates to hybrid instruments, interest rate and other components includes interest rate, foreign exchange and equity contract risks.

[2] During the three months ended June 30, 2016, the gain in the credit risk component for hybrid instruments was attributable to the widening of credit spreads on structured deposits, partially offset by the tightening of our own credits spreads related to structured notes. During the six months ended June 30, 2016, the gains in the credit risk component for hybrid instruments was attributable to the widening of our own credit spreads related to structured notes, partially offset by the tightening of credit spreads on structured deposits. During the three and six months ended June 30, 2015, the losses in the credit risk component for hybrid instruments were attributable to changes in estimates associated with the valuation techniques used to measure the fair value of certain structured notes and deposits, partially offset by the widening of credit spreads on structured deposits and, in the year-to-date period, the widening of our own credit spreads related to structured notes.

[3] During the three months ended June 30, 2016, the loss in the credit risk component for long-term debt was attributable to the tightening of our own credit spreads while the gains during the six months ended June 30, 2016 was attributable to the widening of our own credit spreads. During the three and six months ended June 30, 2015, the gains in the credit risk component for long-term debt were attributable to the widening of our own credit spreads.