Fair Value Option - Components of Gain (Loss) on Instruments at Fair Value and Related Derivatives (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Mark-to-market on the related derivatives	$ (30)		$ 246		$ 563		$ 159
Gain (loss) on instruments designated at fair value and related derivatives	36		(6)		20		82
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	47	[1]	(240)	[1]	(579)	[1]	(169)	[1]
Credit risk component, total	22	[2],[3]	(24)	[2],[3]	28	[2],[3]	95	[2],[3]
Total mark-to-market on financial instruments designated at fair value	69		(264)		(551)		(74)
Net realized loss on the financial instruments					0		(8)
Mark-to-market on the related derivatives	(50)		241		520		115
Net Realized Gain Losses On Related Long Term Debt Derivatives	17		17		51		49
Gain (loss) on instruments designated at fair value and related derivatives	36		(6)		20		82
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	[1]	0	[1]	1	[1]	0	[1]
Credit risk component, assets	0	[2],[3]	0	[2],[3]	0	[2],[3]	21	[2],[3]
Total mark-to-market on financial instruments designated at fair value	1		0		1		21
Net realized loss on the financial instruments					0		(8)
Mark-to-market on the related derivatives	0		0		0		0
Net Realized Gain Losses On Related Long Term Debt Derivatives	0		0		0		0
Gain (loss) on instruments designated at fair value and related derivatives	1		0		1		13
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	(24)	[1]	40	[1]	(167)	[1]	223	[1]
Credit risk component, liabilities	7	[2],[3]	(63)	[2],[3]	(20)	[2],[3]	(52)	[2],[3]
Total mark-to-market on financial instruments designated at fair value	(17)		(23)		(187)		171
Net realized loss on the financial instruments					0		0
Mark-to-market on the related derivatives	14		(39)		134		(229)
Net Realized Gain Losses On Related Long Term Debt Derivatives	17		17		51		49
Gain (loss) on instruments designated at fair value and related derivatives	14		(45)		(2)		(9)
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	70	[1]	(280)	[1]	(413)	[1]	(392)	[1]
Credit risk component, liabilities	15	[2],[3]	39	[2],[3]	48	[2],[3]	126	[2],[3]
Total mark-to-market on financial instruments designated at fair value	85		(241)		(365)		(266)
Net realized loss on the financial instruments					0		0
Mark-to-market on the related derivatives	(64)		280		386		344
Net Realized Gain Losses On Related Long Term Debt Derivatives	0		0		0		0
Gain (loss) on instruments designated at fair value and related derivatives	$ 21		$ 39		$ 21		$ 78

[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 and nine months September 30, 2014 and 2013, the gains in the credit risk component for hybrid instruments are attributable primarily to the widening of credit spreads on structured deposits and structured notes.

[3] During the three months ended September 30, 2014, the gain in the credit risk component for long-term debt is attributable to the widening of our own credit spreads while the loss in the nine months ended September 30, 2014, is attributable to the tightening of our own credit spreads.