Loans - Loan Portfolio Composition and Aging Analysis (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	$ 171,351	$ 162,816
30-59 Days	2,582	2,617
60-89 Days	1,337	1,344
Greater than 90 Days	1,637	1,872
Total Delinquent Loans	5,556	5,833
Acquired Loans	24,685	28,550
Total loans held for investment	201,592	197,199	191,814
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Current (as percent)	85.00%	82.56%
30-59 Days (as percent)	1.28%	1.33%
60-89 Days (as percent)	0.67%	0.68%
Greater than 90 Days (as percent)	0.81%	0.95%
Financing Receivable, Percent Past Due	2.76%	2.96%
Acquired Loans (as percent)	12.24%	14.48%
Total Loans (as percent)	100.00%	100.00%
Credit Card
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	77,950	78,361
30-59 Days	899	919
60-89 Days	607	634
Greater than 90 Days	1,147	1,328
Total Delinquent Loans	2,653	2,881
Acquired Loans	28	63
Total loans held for investment	80,631	81,305
Financing Receivable, Recorded Investment, Aging, Percent of Total Loan [Abstract]
Greater than 90 Days (as percent)	1.42%	1.63%
Financing Receivable, Percent Past Due	3.29%	3.54%
Credit Card | Domestic
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	70,768	70,678
30-59 Days	781	778
60-89 Days	533	549
Greater than 90 Days	1,033	1,187
Total Delinquent Loans	2,347	2,514
Acquired Loans	28	63
Total loans held for investment	73,143	73,255
Credit Card | International
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	7,182	7,683
30-59 Days	118	141
60-89 Days	74	85
Greater than 90 Days	114	141
Total Delinquent Loans	306	367
Acquired Loans	0	0
Total loans held for investment	7,488	8,050
Credit Card | Installment loans | Domestic
Financing Receivable, Recorded Investment, Aging [Abstract]
Total loans held for investment	171	323
Consumer Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	43,902	39,787
30-59 Days	1,620	1,600
60-89 Days	702	694
Greater than 90 Days	390	456
Total Delinquent Loans	2,712	2,750
Acquired Loans	24,447	28,225
Total loans held for investment	71,061	70,762
Consumer Banking | Auto
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	33,849	29,477
30-59 Days	1,557	1,519
60-89 Days	670	662
Greater than 90 Days	177	194
Total Delinquent Loans	2,404	2,375
Acquired Loans	1	5
Total loans held for investment	36,254	31,857
Consumer Banking | Home loan
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	6,527	6,775
30-59 Days	48	60
60-89 Days	25	24
Greater than 90 Days	204	239
Total Delinquent Loans	277	323
Acquired Loans	24,399	28,184
Total loans held for investment	31,203	35,282
Consumer Banking | Retail banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	3,526	3,535
30-59 Days	15	21
60-89 Days	7	8
Greater than 90 Days	9	23
Total Delinquent Loans	31	52
Acquired Loans	47	36
Total loans held for investment	3,604	3,623
Commercial Banking
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	49,401	44,566
30-59 Days	60	94
60-89 Days	26	14
Greater than 90 Days	91	75
Total Delinquent Loans	177	183
Acquired Loans	210	262
Total loans held for investment	49,788	45,011
Commercial Banking | Total commercial lending
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	48,587	43,625
30-59 Days	55	86
60-89 Days	24	12
Greater than 90 Days	90	74
Total Delinquent Loans	169	172
Acquired Loans	210	262
Total loans held for investment	48,966	44,059
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	22,769	20,602
30-59 Days	11	17
60-89 Days	12	11
Greater than 90 Days	40	36
Total Delinquent Loans	63	64
Acquired Loans	63	84
Total loans held for investment	22,895	20,750
Commercial Banking | Commercial and industrial
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	25,818	23,023
30-59 Days	44	69
60-89 Days	12	1
Greater than 90 Days	50	38
Total Delinquent Loans	106	108
Acquired Loans	147	178
Total loans held for investment	26,071	23,309
Commercial Banking | Construction loans
Financing Receivable, Recorded Investment, Aging [Abstract]
Total loans held for investment	2,200	2,000
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	814	941
30-59 Days	5	8
60-89 Days	2	2
Greater than 90 Days	1	1
Total Delinquent Loans	8	11
Acquired Loans	0	0
Total loans held for investment	822	952
Other
Financing Receivable, Recorded Investment, Aging [Abstract]
Current	98	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	$ 112	$ 121