Fair Value Option - Gains and Losses on Other Financial Assets and Financial Liabilities at Fair Value (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Unsecured Short-Term Borrowings Including Current Portion of Unsecured Long-Term Borrowings at Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains/(Losses) on the embedded derivative component of hybrid financial instruments	$ (850)	$ 1,840	$ (782)	$ 925
Unsecured Long-Term Borrowings at Fair Value [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Gains/(Losses) on the embedded derivative component of hybrid financial instruments	$ 28	$ 112	$ (420)	$ 645