Fair Value Option - Gains and Losses on Other Financial Assets and Financial Liabilities at Fair Value (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
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	$ (860)	$ 205
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	$ (144)	$ (338)