Investment Securities - Schedule of Credit Losses Related to Debt Securities Recognized in Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Credit loss component, beginning of period	$ 199	$ 175	$ 160
Additions:
Initial credit impairment	3	7	5
Subsequent credit impairment	8	18	12
Total additions	11	25	17
Reductions due to payoffs, disposals, transfers and other	(3)	(1)	(2)
Credit loss component, end of period	$ 207	$ 199	$ 175