Fair Value Option - Components of Gain (Loss) on Debt Designated at Fair Value and Related Derivatives (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Mark-to-market on debt designated at fair value :
Interest rate component	[1]	$ 24	$ 33	$ 42	$ 146
Credit risk component	[1]	(27)	1	(8)	35
Total mark-to-market on debt designated at fair value	[1]	(3)	34	34	181
Mark-to-market on the related derivatives	[1],[2]	(16)	(41)	(40)	(172)
Net realized gains on the related derivatives	[1]	11	41	38	158
Gain (loss) on debt designated at fair value and related derivatives		(8)	34	32	167
Foreign currency translation gains (losses) recorded in derivatives		(22)	(1)	(68)	206
Offsetting gains (losses) recorded in derivative related income (expense)		$ 22	$ 1	$ 68	$ (206)

[1] The derivatives associated with debt designated at fair value are economic hedges but do not qualify for hedge accounting. See Note 6, "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 $22 million and a loss of $1 million for the three months ended September 30, 2016 and 2015, respectively, and a loss of $68 million and a gain of $206 million for the nine months ended September 30, 2016 and 2015, respectively. Offsetting gains (losses) recorded in derivative related income (expense) associated with the related derivatives was a gain of $22 million and a gain of $1 million for the three months ended September 30, 2016 and 2015, respectively, and a gain of $68 million and a loss of $206 million for the nine months ended September 30, 2016 and 2015, respectively.