Allowance for Loan and Lease Losses - Components of Allowance for Loan and Lease Losses by Impairment Methodology (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	$ 3,895		$ 3,947
Asset-specific	294		330
Acquired Loans	23		38
Total allowance for loan and lease losses	4,212		4,315
Loans held for investment by impairment methodology:
Collectively evaluated	175,221		166,891
Asset-specific	1,686		1,758
Acquired Loans	24,685		28,550
Total loans held for investment	201,592		197,199	191,814
Allowance as a percentage of period-end loans held for investment	2.09%		2.19%
Credit Card
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	2,835		2,953
Asset-specific	222		261
Acquired Loans	0		0
Total allowance for loan and lease losses	3,057	2,858	3,214	3,245	3,349	3,979
Loans held for investment by impairment methodology:
Collectively evaluated	79,897		80,462
Asset-specific	706		780
Acquired Loans	28		63
Total loans held for investment	80,631		81,305
Allowance as a percentage of period-end loans held for investment	3.79%		3.95%
Consumer Banking
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	709		670
Asset-specific	40		44
Acquired Loans	23		38
Total allowance for loan and lease losses	772	765	752	733	702	711
Loans held for investment by impairment methodology:
Collectively evaluated	45,999		41,888
Asset-specific	615		649
Acquired Loans	24,447		28,225
Total loans held for investment	71,061		70,762
Allowance as a percentage of period-end loans held for investment	1.09%		1.06%
Consumer Banking | Auto
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	642		590
Asset-specific	18		16
Acquired Loans	0		0
Total allowance for loan and lease losses	660	642	606	585	537	486
Loans held for investment by impairment methodology:
Collectively evaluated	36,049		31,683
Asset-specific	204		169
Acquired Loans	1		5
Total loans held for investment	36,254		31,857
Allowance as a percentage of period-end loans held for investment	1.82%		1.90%
Consumer Banking | Home loan
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	17		27
Asset-specific	16		18
Acquired Loans	22		38
Total allowance for loan and lease losses	55	67	83	78	79	113
Loans held for investment by impairment methodology:
Collectively evaluated	6,444		6,704
Asset-specific	360		394
Acquired Loans	24,399		28,184
Total loans held for investment	31,203		35,282
Allowance as a percentage of period-end loans held for investment	0.18%		0.24%
Consumer Banking | Retail banking
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	50		53
Asset-specific	6		10
Acquired Loans	1		0
Total allowance for loan and lease losses	57	56	63	70	86	112
Loans held for investment by impairment methodology:
Collectively evaluated	3,506		3,501
Asset-specific	51		86
Acquired Loans	47		36
Total loans held for investment	3,604		3,623
Allowance as a percentage of period-end loans held for investment	1.57%		1.74%
Commercial Banking
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	346		313
Asset-specific	32		25
Acquired Loans	0		0
Total allowance for loan and lease losses	378	368	338	341	338	433
Loans held for investment by impairment methodology:
Collectively evaluated	49,213		44,420
Asset-specific	365		329
Acquired Loans	210		262
Total loans held for investment	49,788		45,011
Allowance as a percentage of period-end loans held for investment	0.76%		0.75%
Other
Allowance for loan and lease losses by impairment methodology:
Collectively evaluated	5		11
Asset-specific	0		0
Acquired Loans	0		0
Total allowance for loan and lease losses	5	7	11	14	18	33
Loans held for investment by impairment methodology:
Collectively evaluated	112		121
Asset-specific	0		0
Acquired Loans	0		0
Total loans held for investment	$ 112		$ 121
Allowance as a percentage of period-end loans held for investment	5.00%		9.09%