Allowance for Loan and Lease Losses - Summary of Changes in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period			$ 6,503
Balance at end of the period	$ 7,170		7,170
Total Allowance
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	6,984	$ 5,416	6,503	$ 5,130
Charge-offs	(2,102)	(1,528)	(4,093)	(3,090)
Recoveries	484	373	965	757
Net charge-offs	(1,618)	(1,155)	(3,128)	(2,333)
Provision (benefit) for loan and lease losses	1,801	1,649	3,789	3,118
Allowance build (release) for loan and lease losses	183	494	661	785
Other changes	3	(29)	6	(34)
Balance at end of the period	7,170	5,881	7,170	5,881
Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	140	226	136	168
Provision (benefit) for loan and lease losses	(1)	(57)	3	1
Balance at end of the period	139	169	139	169
Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	7,309	6,050	7,309	6,050
Credit Card Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	5,058	3,785	4,606	3,654
Charge-offs	(1,572)	(1,215)	(3,173)	(2,437)
Recoveries	316	266	646	538
Net charge-offs	(1,256)	(949)	(2,527)	(1,899)
Provision (benefit) for loan and lease losses	1,397	1,261	3,114	2,332
Allowance build (release) for loan and lease losses	141	312	587	433
Other changes	11	(11)	17	(1)
Balance at end of the period	5,210	4,086	5,210	4,086
Credit Card Portfolio Segment [Member] | Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	0	0	0	0
Provision (benefit) for loan and lease losses	0	0	0	0
Balance at end of the period	0	0	0	0
Credit Card Portfolio Segment [Member] | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	5,210	4,086	5,210	4,086
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	1,163	914	1,102	868
Charge-offs	(390)	(248)	(754)	(539)
Recoveries	158	102	304	210
Net charge-offs	(232)	(146)	(450)	(329)
Provision (benefit) for loan and lease losses	268	204	547	433
Allowance build (release) for loan and lease losses	36	58	97	104
Other changes	0	0	0	0
Balance at end of the period	1,199	972	1,199	972
Consumer Portfolio Segment [Member] | Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	7	8	7	7
Provision (benefit) for loan and lease losses	0	0	0	1
Balance at end of the period	7	8	7	8
Consumer Portfolio Segment [Member] | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	1,206	980	1,206	980
Commercial Banking
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	761	714	793	604
Charge-offs	(140)	(64)	(166)	(112)
Recoveries	4	4	7	6
Net charge-offs	(136)	(60)	(159)	(106)
Provision (benefit) for loan and lease losses	141	185	135	356
Allowance build (release) for loan and lease losses	5	125	(24)	250
Other changes	(8)	(18)	(11)	(33)
Balance at end of the period	758	821	758	821
Commercial Banking | Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	133	218	129	161
Provision (benefit) for loan and lease losses	(1)	(57)	3	0
Balance at end of the period	132	161	132	161
Commercial Banking | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	890	982	890	982
Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	2	3	2	4
Charge-offs	0	(1)	0	(2)
Recoveries	6	1	8	3
Net charge-offs	6	0	8	1
Provision (benefit) for loan and lease losses	(5)	(1)	(7)	(3)
Allowance build (release) for loan and lease losses	1	(1)	1	(2)
Other changes	0	0	0	0
Balance at end of the period	3	2	3	2
Other | Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	0	0	0	0
Provision (benefit) for loan and lease losses	0	0	0	0
Balance at end of the period	0	0	0	0
Other | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	$ 3	$ 2	$ 3	$ 2