Investment Securities - Schedule of Credit Losses Related to Debt Securities Recognized in Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Credit loss component, beginning of period	$ 175	$ 160	$ 120
Additions:
Initial credit impairment	7	5	14
Subsequent credit impairment	18	12	27
Total additions	25	17	41
Reductions due to payoffs, disposals, transfers and other	(1)	(2)	(1)
Credit loss component, end of period	$ 199	$ 175	$ 160