Stockholders' Equity - Components of Other Comprehensive Income Loss and Related Tax Impact (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Before Tax
Net unrealized gains (losses) on securities available for sale	$ 23	$ (254)	$ (393)
Net changes in securities held to maturity	150	164	151
Net unrealized gains (losses) on cash flow hedges	(325)	(315)	175
Foreign currency translation adjustments	3	86	(86)
Other	38	10	(14)
Other comprehensive income before taxes	(111)	(309)	(167)
Provision (Benefit)
Net unrealized gains (losses) on securities available for sale	2	(88)	(145)
Net changes in securities held to maturity	53	60	55
Net unrealized gains (losses) on cash flow hedges	(122)	(117)	65
Foreign currency translation adjustments	(81)	165	49
Other	14	4	(5)
Other comprehensive income (loss), provision (benefit)	(134)	24	19
After Tax
Net unrealized gains (losses) on securities available for sale	21	(166)	(248)
Net changes in securities held to maturity	97	104	96
Net unrealized gains (losses) on cash flow hedges	(203)	(198)	110
Foreign currency translation adjustments	84	(79)	(135)
Other	24	6	(9)
Other comprehensive income (loss), net of tax	$ 23	$ (333)	$ (186)

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