Investment Securities - Schedule of Credit Losses Related to Debt Securities Recognized in Earnings (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Credit loss component, beginning of period	$ 160	$ 120	$ 68
Additions:
Initial credit impairment	5	14	22
Subsequent credit impairment	12	27	30
Total additions	17	41	52
Reduction due to payoffs, disposals, transfers & other	(2)	(1)	0
Credit loss component, end of period	$ 175	$ 160	$ 120