Business Segments - Schedule of Segment Results and Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 5,473	$ 5,093	$ 10,947	$ 10,149
Non-interest income	1,231	1,161	2,292	2,325
Total net revenue	6,704	6,254	13,239	12,474
Provision for loan, lease and other losses	1,800	1,592	3,792	3,119
Total non-interest expense	3,414	3,295	6,848	6,518
Income from continuing operations before income taxes	1,490	1,367	2,599	2,837
Income tax provision (benefit)	443	424	757	876
Income from continuing operations, net of tax	1,047	943	1,842	1,961
Loans held for investment	244,302	234,603	244,302	234,603	$ 245,586
Total deposits	239,763	221,059	239,763	221,059	236,768
Operating Segments | Credit Card
Segment Reporting Information [Line Items]
Net interest income	3,294	3,045	6,640	6,078
Non-interest income	875	859	1,613	1,706
Total net revenue	4,169	3,904	8,253	7,784
Provision for loan, lease and other losses	1,397	1,261	3,114	2,332
Total non-interest expense	1,918	1,883	3,847	3,746
Income from continuing operations before income taxes	854	760	1,292	1,706
Income tax provision (benefit)	301	276	468	613
Income from continuing operations, net of tax	553	484	824	1,093
Loans held for investment	101,590	96,904	101,590	96,904
Total deposits	0	0	0	0
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	1,578	1,439	3,095	2,859
Non-interest income	183	175	378	366
Total net revenue	1,761	1,614	3,473	3,225
Provision for loan, lease and other losses	268	204	547	434
Total non-interest expense	1,059	1,006	2,101	1,996
Income from continuing operations before income taxes	434	404	825	795
Income tax provision (benefit)	158	147	301	289
Income from continuing operations, net of tax	276	257	524	506
Loans held for investment	74,973	71,415	74,973	71,415	66,916
Total deposits	186,607	176,340	186,607	176,340
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	569	559	1,135	1,096
Non-interest income	183	129	341	247
Total net revenue	752	688	1,476	1,343
Provision for loan, lease and other losses	140	128	138	356
Total non-interest expense	381	343	772	665
Income from continuing operations before income taxes	231	217	566	322
Income tax provision (benefit)	85	79	207	117
Income from continuing operations, net of tax	146	138	359	205
Loans held for investment	67,672	66,202	67,672	66,202	$ 66,916
Total deposits	33,153	34,281	33,153	34,281
Other
Segment Reporting Information [Line Items]
Net interest income	32	50	77	116
Non-interest income	(10)	(2)	(40)	6
Total net revenue	22	48	37	122
Provision for loan, lease and other losses	(5)	(1)	(7)	(3)
Total non-interest expense	56	63	128	111
Income from continuing operations before income taxes	(29)	(14)	(84)	14
Income tax provision (benefit)	(101)	(78)	(219)	(143)
Income from continuing operations, net of tax	72	64	135	157
Loans held for investment	67	82	67	82
Total deposits	$ 20,003	$ 10,438	$ 20,003	$ 10,438