Allowance for Loan and Lease Losses - Summary of Changes in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	$ 5,130
Balance at end of the period	6,503	$ 5,130
Total Allowance
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	5,130	4,383	$ 4,315
Provision (benefit) for loan and lease losses	6,491	4,490	3,515
Charge-offs	(6,555)	(5,193)	(4,996)
Recoveries	1,493	1,498	1,582
Net charge-offs	(5,062)	(3,695)	(3,414)
Other changes	(56)	(48)	(33)
Balance at end of the period	6,503	5,130	4,383
Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	168	113	87
Provision (benefit) for loan and lease losses	(32)	46	26
Other changes	0	9
Balance at end of the period	136	168	113
Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	5,298	4,496
Balance at end of the period	6,639	5,298	4,496
Credit Card Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	3,654	3,204	3,214
Provision (benefit) for loan and lease losses	4,926	3,417	2,750
Charge-offs	(5,019)	(4,028)	(3,963)
Recoveries	1,066	1,110	1,235
Net charge-offs	(3,953)	(2,918)	(2,728)
Other changes	(21)	(49)	(32)
Balance at end of the period	4,606	3,654	3,204
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
Provision (benefit) for loan and lease losses	0	0	0
Other changes	0	0
Balance at end of the period	0	0	0
Credit Card Portfolio Segment [Member] | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	3,654	3,204
Balance at end of the period	4,606	3,654	3,204
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	868	779	752
Provision (benefit) for loan and lease losses	1,055	819	703
Charge-offs	(1,226)	(1,082)	(989)
Recoveries	406	351	314
Net charge-offs	(820)	(731)	(675)
Other changes	(1)	1	(1)
Balance at end of the period	1,102	868	779
Consumer Portfolio Segment [Member] | Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	7	7	7
Provision (benefit) for loan and lease losses	0	0	0
Other changes	0	0
Balance at end of the period	7	7	7
Consumer Portfolio Segment [Member] | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	875	786
Balance at end of the period	1,109	875	786
Commercial Banking
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	604	395	338
Provision (benefit) for loan and lease losses	515	256	67
Charge-offs	(307)	(76)	(34)
Recoveries	15	29	24
Net charge-offs	(292)	(47)	(10)
Other changes	(34)	0	0
Balance at end of the period	793	604	395
Commercial Banking | Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	161	106	80
Provision (benefit) for loan and lease losses	(32)	46	26
Other changes	0	9
Balance at end of the period	129	161	106
Commercial Banking | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	765	501
Balance at end of the period	922	765	501
Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	4	5	11
Provision (benefit) for loan and lease losses	(5)	(2)	(5)
Charge-offs	(3)	(7)	(10)
Recoveries	6	8	9
Net charge-offs	3	1	(1)
Other changes	0	0	0
Balance at end of the period	2	4	5
Other | Unfunded Lending Commitments Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	0	0	0
Provision (benefit) for loan and lease losses	0	0	0
Other changes	0	0
Balance at end of the period	0	0	0
Other | Combined Allowance & Unfunded Reserve
Allowance for Loan and Lease Losses [Roll Forward]
Balance as beginning of the period	4	5
Balance at end of the period	$ 2	$ 4	$ 5