Investment Securities - Schedule of Credit Losses Related to Debt Securities Recognized in Earnings (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Credit loss component, beginning of period	$ 199	$ 175
Additions:
Initial credit impairment	0	5
Subsequent credit impairment	6	10
Total additions	6	15
Reductions due to payoffs, disposals, transfers and other	(1)	0
Credit loss component, end of period	$ 204	$ 190