Allowance for Loan and Lease Losses - Summary of Changes in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period			$ 4,383
Balance at end of the period	$ 4,847		4,847
Total Allowance
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	4,676	$ 3,998	4,383	$ 4,315
Provision for credit losses	1,077	988	3,119	2,412
Charge-offs	(1,263)	(1,155)	(3,773)	(3,702)
Recoveries	373	399	1,156	1,203
Net charge-offs	(890)	(756)	(2,617)	(2,499)
Other changes	(16)	(18)	(38)	(16)
Balance at end of the period	4,847	4,212	4,847	4,212
Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	135	102	113	87
Provision for credit losses	15	5	37	20
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	150	107	150	107
Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	4,811	4,100	4,496	4,402
Provision for credit losses	1,092	993	3,156	2,432
Charge-offs	(1,263)	(1,155)	(3,773)	(3,702)
Recoveries	373	399	1,156	1,203
Net charge-offs	(890)	(756)	(2,617)	(2,499)
Other changes	(16)	(18)	(38)	(16)
Balance at end of the period	4,997	4,319	4,997	4,319
Credit Card Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	3,324	2,858	3,204	3,214
Provision for credit losses	831	787	2,395	1,894
Charge-offs	(930)	(885)	(2,940)	(2,975)
Recoveries	275	313	863	938
Net charge-offs	(655)	(572)	(2,077)	(2,037)
Other changes	(16)	(16)	(38)	(14)
Balance at end of the period	3,484	3,057	3,484	3,057
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	875	765	779	752
Provision for credit losses	188	198	579	481
Charge-offs	(286)	(264)	(761)	(700)
Recoveries	83	74	263	240
Net charge-offs	(203)	(190)	(498)	(460)
Other changes	0	(1)	0	(1)
Balance at end of the period	860	772	860	772
Consumer Portfolio Segment [Member] | Auto
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	744	642	661	606
Provision for credit losses	178	194	530	475
Charge-offs	(264)	(245)	(700)	(633)
Recoveries	76	69	243	212
Net charge-offs	(188)	(176)	(457)	(421)
Other changes	0	0	0	0
Balance at end of the period	734	660	734	660
Consumer Portfolio Segment [Member] | Home loan
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	65	67	62	83
Provision for credit losses	(4)	(9)	4	(15)
Charge-offs	(5)	(4)	(14)	(23)
Recoveries	4	2	8	11
Net charge-offs	(1)	(2)	(6)	(12)
Other changes	0	(1)	0	(1)
Balance at end of the period	60	55	60	55
Consumer Portfolio Segment [Member] | Retail banking
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	66	56	56	63
Provision for credit losses	14	13	45	21
Charge-offs	(17)	(15)	(47)	(44)
Recoveries	3	3	12	17
Net charge-offs	(14)	(12)	(35)	(27)
Other changes	0	0	0	0
Balance at end of the period	66	57	66	57
Commercial Banking
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	472	368	395	338
Provision for credit losses	60	4	147	41
Charge-offs	(47)	(4)	(67)	(19)
Recoveries	14	10	24	18
Net charge-offs	(33)	6	(43)	(1)
Other changes	0	0	0	0
Balance at end of the period	499	378	499	378
Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	5	7	5	11
Provision for credit losses	(2)	(1)	(2)	(4)
Charge-offs	0	(2)	(5)	(8)
Recoveries	1	2	6	7
Net charge-offs	1	0	1	(1)
Other changes	0	(1)	0	(1)
Balance at end of the period	$ 4	$ 5	$ 4	$ 5