Fair Value Option - Changes in Fair Value of the Loans and Long-Term Debt and the Location of the Changes (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Investment and other income | Loans Receivable
Fair Value, Option, Quantitative Disclosures [Line Items]
Changes in the fair value	[1]	$ 18	$ 3	$ 2
Foreign exchange and other trading revenue | Long-term debt
Fair Value, Option, Quantitative Disclosures [Line Items]
Changes in the fair value	[1]	$ (13)	$ 3	$ (8)

[1] (a)The changes in fair value of the loans and long-term debt are approximately offset by economic hedges included in foreign exchange and other trading revenue.