Investment Securities - Schedule of Credit Losses Related to Debt Securities Recognized in Earnings (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Credit loss component, beginning of period	$ 206	$ 204	$ 207	$ 199
Additions:
Initial credit impairment	0	1	0	1
Subsequent credit impairment	1	1	1	7
Total additions	1	2	1	8
Reductions due to payoffs, disposals, transfers and other	0	(2)	(1)	(3)
Credit loss component, end of period	$ 207	$ 204	$ 207	$ 204