Fair Value Option - Components of Gain on Instruments at Fair Value and Related Derivatives (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	$ (235)	[1]	$ (253)	[1]
Credit risk component	45	[2],[3]	12	[2],[3]
Total mark-to-market on financial instruments designated at fair value	(190)		(241)
Net realized loss on the financial instruments	0		(8)
Mark-to-market on the related derivatives	201		206
Net realized gain on the related long-term debt derivatives	17		16
Gain (loss) on instruments designated at fair value and related derivatives	28		(27)
Loans [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	0	[1]	0	[1]
Credit risk component	0	[2],[3]	21	[2],[3]
Total mark-to-market on financial instruments designated at fair value	0		21
Net realized loss on the financial instruments	0		(8)
Mark-to-market on the related derivatives	0		0
Net realized gain on the related long-term debt derivatives	0		0
Gain (loss) on instruments designated at fair value and related derivatives	0		13
Long-term Debt [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	(82)	[1]	63	[1]
Credit risk component	19	[2],[3]	(42)	[2],[3]
Total mark-to-market on financial instruments designated at fair value	(63)		21
Net realized loss on the financial instruments	0		0
Mark-to-market on the related derivatives	70		(62)
Net realized gain on the related long-term debt derivatives	17		16
Gain (loss) on instruments designated at fair value and related derivatives	24		(25)
Hybrid Instruments [Member]
Components Of Gain On Instruments At Fair Value And Related Derivatives [Line Items]
Interest rate and other components	(153)	[1]	(316)	[1]
Credit risk component	26	[2],[3]	33	[2],[3]
Total mark-to-market on financial instruments designated at fair value	(127)		(283)
Net realized loss on the financial instruments	0		0
Mark-to-market on the related derivatives	131		268
Net realized gain on the related long-term debt derivatives	0		0
Gain (loss) on instruments designated at fair value and related derivatives	$ 4		$ (15)

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

[2] During the first quarter of 2014 and 2013, the gain in the credit risk component for hybrid instruments was attributable primarily to the widening of credit spreads on structured notes.

[3] During the first quarter of 2014, the gain in the credit risk component for long-term debt was attributable to the widening of our own credit spreads, while the loss in the first quarter of 2013 is attributable to