Stockholders' Equity - Reclassifications from AOCI (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	$ 167	$ 157	$ 466	$ 427
Non-interest income - OTTI	(5)	(9)	(27)	(15)
Interest income	4,760	4,497	13,873	13,162
Income from continuing operations before income taxes	1,648	1,661	4,547	5,149
Income tax provision (benefit)	530	536	1,443	1,696
Net income	1,114	1,081	3,130	3,429
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	13	3	39	23
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income [Member] | Securities Available for Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	3	6	4	18
Non-interest income - OTTI	(5)	(9)	(27)	(15)
Income from continuing operations before income taxes	(2)	(3)	(23)	3
Income tax provision (benefit)	0	(1)	(8)	1
Net income	(2)	(2)	(15)	2
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]
Non-interest income	(41)	(35)	(114)	(96)
Income tax provision (benefit)	(16)	(13)	(42)	(40)
Net income	(25)	(22)	(72)	(56)
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	60	47	194	119
Income tax provision (benefit)	23	18	72	45
Net income	37	29	122	74
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	64	54	217	144
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	(4)	(7)	(23)	(25)
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	2	4	10
Income tax provision (benefit)	(1)	4	0	7
Net income	$ 3	$ (2)	$ 4	$ 3