Fair Value Option - Gains and Losses on Other Financial Assets and Financial Liabilities at Fair Value (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value Option Gains/(Losses)	$ (935)	$ 1,915	$ (2,096)	$ 989
Unsecured Short-Term Borrowings Including Current Portion of Unsecured Long-Term Borrowings at Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value Option Gains/(Losses)	(832)	1,845	(773)	947
Unsecured Long-Term Borrowings at Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value Option Gains/(Losses)	(19)	273	(608)	746
Other Liabilities and Accrued Expenses at Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value Option Gains/(Losses)	1	(237)	(86)	(676)
Fair Value Option Other [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair Value Option Gains/(Losses)	$ (85)	$ 34	$ (629)	$ (28)