Fair Value Option - Components of Gain on Instruments at Fair Value and Related Derivatives (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	$ (391)	[1]	$ 324	[1]	$ (626)	[1]	$ 71	[1]
Credit risk component	(39)		107		6	[2],[3]	119	[2],[3]
Total mark-to-market on financial instruments designated at fair value	(430)		431		(620)		190
Net realized loss on the financial instruments					0		(8)
Mark-to-market on the related derivatives	369		(352)		570		(126)
Net realized gain on the related long-term debt derivatives	17		16		34		32
Gain (loss) on instruments designated at fair value and related derivatives	(44)		95		(16)		88
Loans [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	0	[1]	0	[1]	0	[1]	0	[1]
Credit risk component	0		0		0	[2],[3]	21	[2],[3]
Total mark-to-market on financial instruments designated at fair value	0		0		0		21
Net realized loss on the financial instruments					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	0		0		0		13
Long-term Debt [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	(61)	[1]	120	[1]	(143)	[1]	183	[1]
Credit risk component	(46)		53		(27)	[2],[3]	11	[2],[3]
Total mark-to-market on financial instruments designated at fair value	(107)		173		(170)		194
Net realized loss on the financial instruments					0		0
Mark-to-market on the related derivatives	50		(128)		120		(190)
Net realized gain on the related long-term debt derivatives	17		16		34		32
Gain (loss) on instruments designated at fair value and related derivatives	(40)		61		(16)		36
Hybrid Instruments [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	(330)	[1]	204	[1]	(483)	[1]	(112)	[1]
Credit risk component	7		54		33	[2],[3]	87	[2],[3]
Total mark-to-market on financial instruments designated at fair value	(323)		258		(450)		(25)
Net realized loss on the financial instruments					0		0
Mark-to-market on the related derivatives	319		(224)		450		64
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)		$ 34		$ 0		$ 39

[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 six months ended June 30, 2014, the losses in the credit risk component for long-term debt are attributable to the tightening of our own credit spreads while the gains during the three and six months ended June 30, 2013 are attributable to the widening of our own credit spreads.

[3] During the three months ended June 30, 2014, the gains in the credit risk component for hybrid instruments reflect the widening of credit spreads on structured deposits partially offset by the tightening of credit spreads on structured notes. During the six months ended June 30, 2014, the gains in the credit risk component for hybrid instruments are attributable primarily to the widening of credit spreads on structured notes. During the three and six months ended June 30, 2013, the gains in the credit risk component for hybrid instruments are attributable primarily to the widening of credit spreads on structured notes.