Allowance for Loan and Lease Losses - Summary of Changes in Allowance for Loan and Lease Losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2014	Sep. 30, 2013
Allowance for Loan and Lease Losses
Balance as beginning of the period				$ 4,315
Provision for credit losses	993	849		2,432	2,496
Balance at end of the period	4,212			4,212
Reduction in allowance for loan and lease losses			289
Total Allowance
Allowance for Loan and Lease Losses
Balance as beginning of the period	3,998	4,407	5,156	4,315	5,156
Provision for credit losses	988	829		2,412	2,442
Charge-offs	(1,155)	(1,294)		(3,702)	(4,169)
Recoveries	399	377		1,203	1,204
Net charge-offs	(756)	(917)		(2,499)	(2,965)
Other changes	(18)	14		(16)	(300)
Balance at end of the period	4,212	4,333		4,212	4,333
Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses
Balance as beginning of the period	102	69	35	87	35
Provision for credit losses	5	20		20	54
Charge-offs	0	0		0	0
Recoveries	0	0		0	0
Net charge-offs	0	0		0	0
Other changes	0	0		0	0
Balance at end of the period	107	89		107	89
Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses
Balance as beginning of the period	4,100	4,476	5,191	4,402	5,191
Provision for credit losses	993	849		2,432	2,496
Charge-offs	(1,155)	(1,294)		(3,702)	(4,169)
Recoveries	399	377		1,203	1,204
Net charge-offs	(756)	(917)		(2,499)	(2,965)
Other changes	(18)	14		(16)	(300)
Balance at end of the period	4,319	4,422		4,319	4,422
Credit Card
Allowance for Loan and Lease Losses
Balance as beginning of the period	2,858	3,349	3,979	3,214	3,979
Provision for credit losses	787	617		1,894	2,073
Charge-offs	(885)	(1,036)		(2,975)	(3,479)
Recoveries	313	302		938	973
Net charge-offs	(572)	(734)		(2,037)	(2,506)
Other changes	(16)	13		(14)	(301)
Balance at end of the period	3,057	3,245		3,057	3,245
Consumer Banking
Allowance for Loan and Lease Losses
Balance as beginning of the period	765	702	711	752	711
Provision for credit losses	198	202		481	444
Charge-offs	(264)	(234)		(700)	(625)
Recoveries	74	64		240	202
Net charge-offs	(190)	(170)		(460)	(423)
Other changes	(1)	(1)		(1)	1
Balance at end of the period	772	733		772	733
Consumer Banking | Auto
Allowance for Loan and Lease Losses
Balance as beginning of the period	642	537	486	606	486
Provision for credit losses	194	200		475	464
Charge-offs	(245)	(210)		(633)	(545)
Recoveries	69	58		212	179
Net charge-offs	(176)	(152)		(421)	(366)
Other changes	0	0		0	1
Balance at end of the period	660	585		660	585
Consumer Banking | Home loan
Allowance for Loan and Lease Losses
Balance as beginning of the period	67	79	113	83	113
Provision for credit losses	(9)	5		(15)	(22)
Charge-offs	(4)	(6)		(23)	(18)
Recoveries	2	1		11	5
Net charge-offs	(2)	(5)		(12)	(13)
Other changes	(1)	(1)		(1)	0
Balance at end of the period	55	78		55	78
Consumer Banking | Retail banking
Allowance for Loan and Lease Losses
Balance as beginning of the period	56	86	112	63	112
Provision for credit losses	13	(3)		21	2
Charge-offs	(15)	(18)		(44)	(62)
Recoveries	3	5		17	18
Net charge-offs	(12)	(13)		(27)	(44)
Other changes	0	0		0	0
Balance at end of the period	57	70		57	70
Commercial Banking
Allowance for Loan and Lease Losses
Balance as beginning of the period	368	338	433	338	433
Provision for credit losses	4	11		41	(73)
Charge-offs	(4)	(17)		(19)	(43)
Recoveries	10	9		18	24
Net charge-offs	6	(8)		(1)	(19)
Other changes	0	0		0	0
Balance at end of the period	378	341		378	341
Other
Allowance for Loan and Lease Losses
Balance as beginning of the period	7	18	33	11	33
Provision for credit losses	(1)	(1)		(4)	(2)
Charge-offs	(2)	(7)		(8)	(22)
Recoveries	2	2		7	5
Net charge-offs	0	(5)		(1)	(17)
Other changes	(1)	2		(1)	0
Balance at end of the period	$ 5	$ 14		$ 5	$ 14