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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period			$ 7,220
Balance at end of the period	$ 7,133		7,133
Provision for credit losses	1,342	$ 1,276	3,035	$ 2,950
Allowance
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	7,313	7,567	7,220	7,502
Charge-offs	(2,157)	(2,109)	(4,430)	(4,385)
Recoveries	649	650	1,323	1,308
Net charge-offs	(1,508)	(1,459)	(3,107)	(3,077)
Provision (benefit) for loan and lease losses	1,329	1,273	3,013	2,957
Allowance build (release) for loan and lease losses	(179)	(186)	(94)	(120)
Other changes	(1)	(13)	7	(14)
Balance at end of the period	7,133	7,368	7,133	7,368
Reserve for unfunded lending commitments
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	131	114	122	124
Provision (benefit) for loan and lease losses	13	3	22	(7)
Balance at end of the period	144	117	144	117
Combined allowance and reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	7,277	7,485	7,277	7,485
Credit Card
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	5,568	5,726	5,535	5,648
Charge-offs	(1,711)	(1,679)	(3,493)	(3,504)
Recoveries	391	419	809	867
Net charge-offs	(1,320)	(1,260)	(2,684)	(2,637)
Provision (benefit) for loan and lease losses	1,095	1,171	2,484	2,627
Allowance build (release) for loan and lease losses	(225)	(89)	(200)	(10)
Other changes	(1)	(13)	7	(14)
Balance at end of the period	5,342	5,624	5,342	5,624
Credit Card | Reserve for unfunded lending commitments
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 | Combined allowance and reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	5,342	5,624	5,342	5,624
Consumer Banking
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	1,062	1,253	1,048	1,242
Charge-offs	(423)	(414)	(894)	(845)
Recoveries	251	216	501	424
Net charge-offs	(172)	(198)	(393)	(421)
Provision (benefit) for loan and lease losses	165	119	400	353
Allowance build (release) for loan and lease losses	(7)	(79)	7	(68)
Other changes	0	(54)	0	(54)
Balance at end of the period	1,055	1,120	1,055	1,120
Consumer Banking | Reserve for unfunded lending commitments
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	4	6	4	7
Provision (benefit) for loan and lease losses	0	(1)	0	(2)
Balance at end of the period	4	5	4	5
Consumer Banking | Combined allowance and reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	1,059	1,125	1,059	1,125
Consumer Banking | Home loan
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs	0	0	0	1
Commercial Banking
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	683	587	637	611
Charge-offs	(23)	(7)	(43)	(28)
Recoveries	7	14	13	16
Net charge-offs	(16)	7	(30)	(12)
Provision (benefit) for loan and lease losses	69	30	129	25
Allowance build (release) for loan and lease losses	53	37	99	13
Other changes	0	0	0	0
Balance at end of the period	736	624	736	624
Commercial Banking | Reserve for unfunded lending commitments
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	127	108	118	117
Provision (benefit) for loan and lease losses	13	4	22	(5)
Balance at end of the period	140	112	140	112
Commercial Banking | Combined allowance and reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period	$ 876	736	$ 876	736
Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period		1		1
Charge-offs		(9)		(8)
Recoveries		1		1
Net charge-offs		(8)		(7)
Provision (benefit) for loan and lease losses		(47)		(48)
Allowance build (release) for loan and lease losses		(55)		(55)
Other changes		54		54
Balance at end of the period		0		0
Other | Reserve for unfunded lending commitments
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period		0		0
Provision (benefit) for loan and lease losses		0		0
Balance at end of the period		0		0
Other | Combined allowance and reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance at end of the period		0		$ 0
Other | Home loan
Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses		$ (46)