Loans - Credit Card Delinquency Status (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Income (loss) from continuing operations before income taxes	$ 243,131	$ 251,624	$ 262,990
Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	98,548	106,323
Revolving Loans Converted to Term	579	633
Income (loss) from continuing operations before income taxes	99,127	106,956
Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	90,609	97,969
Revolving Loans Converted to Term	490	535
Income (loss) from continuing operations before income taxes	91,099	98,504
International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	7,939	8,354
Revolving Loans Converted to Term	89	98
Income (loss) from continuing operations before income taxes	8,028	8,452
Current | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	88,609	95,629
Revolving Loans Converted to Term	450	487
Income (loss) from continuing operations before income taxes	89,059	96,116
Current | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	7,753	8,152
Revolving Loans Converted to Term	66	66
Income (loss) from continuing operations before income taxes	7,819	8,218
30-59 days | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	511	734
Revolving Loans Converted to Term	16	21
Income (loss) from continuing operations before income taxes	527	755
30-59 days | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	63	79
Revolving Loans Converted to Term	8	11
Income (loss) from continuing operations before income taxes	71	90
60-89 days | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	382	451
Revolving Loans Converted to Term	11	13
Income (loss) from continuing operations before income taxes	393	464
60-89 days | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	40	47
Revolving Loans Converted to Term	7	11
Income (loss) from continuing operations before income taxes	47	58
Greater than 90 days | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,107	1,155
Revolving Loans Converted to Term	13	14
Income (loss) from continuing operations before income taxes	1,120	1,169
Greater than 90 days | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	83	76
Revolving Loans Converted to Term	8	10
Income (loss) from continuing operations before income taxes	$ 91	$ 86