Fair Value Option - Components of Gain (Loss) on Debt Designated at Fair Value and Related Derivatives (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Mark-to-market on debt designated at fair value :
Interest rate component	[1]	$ 64	$ 28	$ 113	$ 64
Credit risk component	[1]	8	(9)	34	(25)
Total mark-to-market on debt designated at fair value	[1]	72	19	147	39
Mark-to-market on the related derivatives	[1],[2]	(54)	(45)	(131)	(102)
Net realized gains on the related derivatives	[1]	56	68	117	136
Gain on debt designated at fair value and related derivatives		74	42	133	73
Foreign currency translation gains (losses) recorded in derivatives		(83)	17	207	15
Offsetting gains (losses) recorded in derivative related income (expense)		$ 83	$ (17)	$ (207)	$ (15)

[1] The derivatives associated with debt designated at fair value are economic hedges but do not qualify for hedge accounting. See Note 7, "Derivative Financial Instruments," for additional discussion of these non-qualifying hedges.

[2] 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 $83 million and a gain of $17 million during the three months ended June 30, 2015 and 2014, respectively, and a gain of $207 million and a gain of $15 million for the six months ended June 30, 2015 and 2014, respectively. Offsetting gains (losses) recorded in derivative related income (expense) associated with the related derivatives was a gain of $83 million and a loss of $17 million during the three months ended June 30, 2015 and 2014, respectively, and a loss of $207 million and a loss of $15 million for the six months ended June 30, 2015 and 2014, respectively.