Derivative Instruments - Summary of Effective Portion of Gains (Losses) Recognized in Other Comprehensive Income (Loss) and Gains (Losses) Reclassified from Other Comprehensive Income (Loss) into Earnings (Detail) - Asset and Liability Management Positions [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flow Hedges [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Losses) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 46	$ (15)	$ (26)
Derivative Instruments, Gains (Losses) Reclassified from Other Comprehensive Income (Loss) into Earnings	(76)	(120)	(115)
Net Investment Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Losses) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 33	$ 101	$ 130