Loans - Loan Portfolio Composition and Aging Analysis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	$ 178,746	$ 162,816
30-59 Days	2,841	2,617
60-89 Days	1,424	1,344
Greater than 90 Days	1,805	1,872
Total Delinquent Loans	6,070	5,833
Acquired Loans	23,500	28,550
Total loans held for investment	208,316	197,199	205,889
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Current (as percent)	85.81%	82.56%
30-59 Days (as percent)	1.36%	1.33%
60-89 Days (as percent)	0.68%	0.68%
Greater than 90 Days (as percent)	0.87%	0.95%
Total Delinquent Loans (as percent)	2.91%	2.96%
Acquired Loans (as percent)	11.28%	14.48%
Total Loans (as percent)	100.00%	100.00%
Credit Card
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	83,021	78,361
30-59 Days	904	919
60-89 Days	636	634
Greater than 90 Days	1,292	1,328
Total Delinquent Loans	2,832	2,881
Acquired Loans	23	63
Total loans held for investment	85,876	81,305
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Greater than 90 Days (as percent)	1.50%	1.63%
Total Delinquent Loans (as percent)	3.30%	3.54%
Credit Card | Domestic
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	75,143	70,678
30-59 Days	790	778
60-89 Days	567	549
Greater than 90 Days	1,181	1,187
Total Delinquent Loans	2,538	2,514
Acquired Loans	23	63
Total loans held for investment	77,704	73,255
Credit Card | International
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	7,878	7,683
30-59 Days	114	141
60-89 Days	69	85
Greater than 90 Days	111	141
Total Delinquent Loans	294	367
Acquired Loans	0	0
Total loans held for investment	8,172	8,050
Credit Card | Installment loans | Domestic
Financing Receivable, Recorded Investment, Aging [Abstract]
Total loans held for investment	144	323
Consumer Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	45,130	39,787
30-59 Days	1,825	1,600
60-89 Days	768	694
Greater than 90 Days	431	456
Total Delinquent Loans	3,024	2,750
Acquired Loans	23,285	28,225
Total loans held for investment	71,439	70,762
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Greater than 90 Days (as percent)	0.60%	0.65%
Total Delinquent Loans (as percent)	4.23%	3.89%
Consumer Banking | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	35,142	29,477
30-59 Days	1,751	1,519
60-89 Days	734	662
Greater than 90 Days	197	194
Total Delinquent Loans	2,682	2,375
Acquired Loans	0	5
Total loans held for investment	37,824	31,857
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Greater than 90 Days (as percent)	0.52%	0.61%
Total Delinquent Loans (as percent)	7.09%	7.46%
Consumer Banking | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	6,492	6,775
30-59 Days	57	60
60-89 Days	27	24
Greater than 90 Days	218	239
Total Delinquent Loans	302	323
Acquired Loans	23,241	28,184
Total loans held for investment	30,035	35,282
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Greater than 90 Days (as percent)	0.73%	0.68%
Total Delinquent Loans (as percent)	1.01%	0.91%
Consumer Banking | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	3,496	3,535
30-59 Days	17	21
60-89 Days	7	8
Greater than 90 Days	16	23
Total Delinquent Loans	40	52
Acquired Loans	44	36
Total loans held for investment	3,580	3,623
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Greater than 90 Days (as percent)	0.44%	0.65%
Total Delinquent Loans (as percent)	1.11%	1.44%
Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	50,498	44,566
30-59 Days	109	94
60-89 Days	18	14
Greater than 90 Days	73	75
Total Delinquent Loans	200	183
Acquired Loans	192	262
Total loans held for investment	50,890	45,011
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	49,727	43,625
30-59 Days	103	86
60-89 Days	17	12
Greater than 90 Days	70	74
Total Delinquent Loans	190	172
Acquired Loans	192	262
Total loans held for investment	50,109	44,059
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	22,974	20,602
30-59 Days	74	17
60-89 Days	7	11
Greater than 90 Days	36	36
Total Delinquent Loans	117	64
Acquired Loans	46	84
Total loans held for investment	23,137	20,750
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	26,753	23,023
30-59 Days	29	69
60-89 Days	10	1
Greater than 90 Days	34	38
Total Delinquent Loans	73	108
Acquired Loans	146	178
Total loans held for investment	26,972	23,309
Commercial Banking | Construction loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Total loans held for investment	2,300	2,000
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	771	941
30-59 Days	6	8
60-89 Days	1	2
Greater than 90 Days	3	1
Total Delinquent Loans	10	11
Acquired Loans	0	0
Total loans held for investment	781	952
Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	97	102
30-59 Days	3	4
60-89 Days	2	2
Greater than 90 Days	9	13
Total Delinquent Loans	14	19
Acquired Loans	0	0
Total loans held for investment	$ 111	$ 121