Business Segments - Schedule of Segment Results and Reconciliation (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net interest income	$ 4,576	$ 4,350
Non-interest income	1,071	1,020
Total net revenue	5,647	5,370
Provision for credit losses	935	735
Amortization of intangibles	110	143
Other non-interest expense	2,939	2,798
Total non-interest expense	3,049	2,932
Income from continuing operations before income taxes	1,663	1,703
Income tax (benefit)	529	579
Income from continuing operations, net of tax	1,134	1,124
Loans held for investment	203,978	192,941	208,316
Total deposits	210,440	208,324	205,548
Operating Segments | Credit Card
Segment Reporting Information [Line Items]
Net interest income	2,666	2,525
Non-interest income	816	785
Total net revenue	3,482	3,310
Provision for credit losses	669	558
Other non-interest expense	1,692	1,628
Total non-interest expense	1,776	1,726
Income from continuing operations before income taxes	1,037	1,026
Income tax (benefit)	369	358
Income from continuing operations, net of tax	668	668
Loans held for investment	81,754	75,850
Total deposits	0	0
Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income	1,434	1,433
Non-interest income	158	150
Total net revenue	1,592	1,583
Provision for credit losses	206	140
Other non-interest expense	948	900
Total non-interest expense	970	930
Income from continuing operations before income taxes	416	513
Income tax (benefit)	150	183
Income from continuing operations, net of tax	266	330
Loans held for investment	71,379	70,727
Total deposits	172,502	171,529
Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income	461	421
Non-interest income	114	87
Total net revenue	575	508
Provision for credit losses	60	40
Other non-interest expense	268	249
Total non-interest expense	272	255
Income from continuing operations before income taxes	243	213
Income tax (benefit)	88	76
Income from continuing operations, net of tax	155	137
Loans held for investment	50,741	46,230
Total deposits	32,575	31,485
Other
Segment Reporting Information [Line Items]
Net interest income	15	(29)
Non-interest income	(17)	(2)
Total net revenue	(2)	(31)
Provision for credit losses	0	(3)
Other non-interest expense	31	21
Total non-interest expense	31	21
Income from continuing operations before income taxes	(33)	(49)
Income tax (benefit)	(78)	(38)
Income from continuing operations, net of tax	45	(11)
Loans held for investment	104	134
Total deposits	5,363	5,310
Purchased credit card relationship intangibles (“PCCR”)
Segment Reporting Information [Line Items]
Amortization of intangibles	84	98
Purchased credit card relationship intangibles (“PCCR”) | Operating Segments | Credit Card
Segment Reporting Information [Line Items]
Amortization of intangibles	84	98
Purchased credit card relationship intangibles (“PCCR”) | Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Amortization of intangibles	0	0
Purchased credit card relationship intangibles (“PCCR”) | Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Amortization of intangibles	0	0
Purchased credit card relationship intangibles (“PCCR”) | Other
Segment Reporting Information [Line Items]
Amortization of intangibles	0	0
Core deposit intangibles
Segment Reporting Information [Line Items]
Amortization of intangibles	26	36
Core deposit intangibles | Operating Segments | Credit Card
Segment Reporting Information [Line Items]
Amortization of intangibles	0	0
Core deposit intangibles | Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Amortization of intangibles	22	30
Core deposit intangibles | Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Amortization of intangibles	4	6
Core deposit intangibles | Other
Segment Reporting Information [Line Items]
Amortization of intangibles	0	0
PCCR and core deposits
Segment Reporting Information [Line Items]
Amortization of intangibles	110	134
PCCR and core deposits | Operating Segments | Credit Card
Segment Reporting Information [Line Items]
Amortization of intangibles	84	98
PCCR and core deposits | Operating Segments | Consumer Banking
Segment Reporting Information [Line Items]
Amortization of intangibles	22	30
PCCR and core deposits | Operating Segments | Commercial Banking
Segment Reporting Information [Line Items]
Amortization of intangibles	4	6
PCCR and core deposits | Other
Segment Reporting Information [Line Items]
Amortization of intangibles	$ 0	$ 0