Stockholders' Equity - Reclassifications from AOCI (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income									$ (541)	$ (491)	$ (421)
Non-interest income - OTTI									(17)	(30)	(24)
Interest income	$ 5,447	$ 5,277	$ 5,093	$ 5,056	$ 4,961	$ 4,760	$ 4,537	$ 4,576	20,873	18,834	17,818
Income from continuing operations before income taxes	1,135	1,512	1,367	1,470	1,334	1,648	1,236	1,663	5,484	5,881	6,569
Income tax provision (benefit)	342	496	424	452	426	530	384	529	1,714	1,869	2,146
Net income	$ 791	$ 1,005	$ 942	$ 1,013	$ 920	$ 1,114	$ 863	$ 1,153	3,751	4,050	4,428
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income									86	62	35
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									10	32	3
Income tax provision (benefit)									(4)	(12)	(1)
Net income									(6)	(20)	(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]
Interest income									(164)	(151)	(131)
Income tax provision (benefit)									(60)	(55)	(55)
Net income									(104)	(96)	(76)
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									310	277	173
Income tax provision (benefit)									115	103	65
Net income									195	174	108
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									306	303	209
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									(2)	(21)	(36)
Interest income									6	(5)	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	5	11
Income tax provision (benefit)									1	1	6
Net income									$ 1	$ 4	$ 5