Fair Value Option - Components of Gain (Loss) on Debt Designated at Fair Value and Related Derivatives (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Mark-to-market on debt designated at fair value :
Total mark-to-market on debt designated at fair value	$ 142		$ 30		$ 187		$ (370)
Mark-to-market on the related derivatives	(107)	[1]	(46)	[1]	(220)	[1]	(162)	[1]
Net realized gains on the related derivatives	84		108		168		228
Gain (loss) on debt designated at fair value and related derivatives	119		92		135		(304)
Interest rate component [Member]
Mark-to-market on debt designated at fair value :
Total mark-to-market on debt designated at fair value	119	[1]	12	[1]	205	[1]	91	[1]
Credit risk contract [Member]
Mark-to-market on debt designated at fair value :
Total mark-to-market on debt designated at fair value	$ 23		$ 18		$ (18)		$ (461)

[1] Mark-to-market on debt designated at fair value and related derivatives excludes market value changes due to fluctuations in foreign currency exchange rates. Foreign currency translation gains (losses) recorded in derivative related income (expense) associated with debt designated at fair value was a loss of $29 million and a gain of $144 million during the three months ended June 30, 2013 and 2012, respectively, and a gain of $81 million and a gain of $84 million during the six months ended June 30, 2013 and 2012, respectively. Offsetting gains (losses) recorded in derivative related income (expense) associated with the related derivatives was a gain of $29 million and a loss of $144 million during the three months ended June 30, 2013 and 2012, respectively, and a loss of $81 million and a loss of $84 million during the six months ended June 30, 2013 and 2012, respectively.