Stockholders' Equity - Components of Other Comprehensive Income Loss and Related Tax Impact (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Before Tax
Net unrealized gains (losses) on securities available for sale	$ 16	$ 17	$ 299	$ 525
Net changes in securities held to maturity	40	44	113	118
Net unrealized gains (losses) on cash flow hedges	(29)	(226)	(61)	601
Foreign currency translation adjustments	11	4	12	70
Other	7	6	19	1
Other comprehensive income before taxes	45	(155)	382	1,315
Provision (Benefit)
Net unrealized gains on securities available for sale	6	7	104	192
Net changes in securities held to maturity	14	16	41	44
Net unrealized gains (losses) on cash flow hedges	(12)	(84)	(23)	223
Foreign currency translation adjustments	(27)	24	(74)	119
Other	3	2	7	0
Other comprehensive income (loss), provision (benefit)	(16)	(35)	55	578
After Tax
Net unrealized gains on securities available for sale	10	10	195	333
Net changes in securities held to maturity	26	28	72	74
Net unrealized gains (losses) on cash flow hedges	(17)	(142)	(38)	378
Foreign currency translation adjustments	38	(20)	86	(49)
Other	4	4	12	1
Other comprehensive income (loss), net of tax	$ 61	$ (120)	$ 327	$ 737