Stockholders' Equity - Reclassifications from AOCI (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	$ (141)	$ (147)	$ (261)	$ (292)
Interest income	5,473	5,093	10,947	10,149
Income from continuing operations before income taxes	1,490	1,367	2,599	2,837
Income tax provision (benefit)	443	424	757	876
Net income	1,036	942	1,846	1,955
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	5	25	24	46
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	(4)	1	(4)	(7)
Income tax provision (benefit)	(2)	0	(2)	(3)
Net income	(2)	1	(2)	(4)
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income [Member] | Securities Held to Maturity
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	(37)	(40)	(73)	(73)
Income tax provision (benefit)	(14)	(15)	(27)	(27)
Net income	(23)	(25)	(46)	(46)
Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	46	79	110	156
Income tax provision (benefit)	17	30	41	58
Net income	29	49	69	98
Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest rate contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	39	78	97	157
Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign exchange contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	0	0	0	(1)
Interest income	7	1	13	0
Other | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	2	0	4	(2)
Income tax provision (benefit)	1	0	1	0
Net income	$ 1	$ 0	$ 3	$ (2)