Loans - Credit Card Delinquency Status (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Income (loss) from continuing operations before income taxes	$ 249,597	$ 251,624	$ 251,512
Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	100,513	106,323
Revolving Loans Converted to Term	504	633
Income (loss) from continuing operations before income taxes	101,017	106,956
Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	94,871	97,969
Revolving Loans Converted to Term	438	535
Income (loss) from continuing operations before income taxes	95,309	98,504
International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	5,642	8,354
Revolving Loans Converted to Term	66	98
Income (loss) from continuing operations before income taxes	5,708	8,452
Current | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	93,304	95,629
Revolving Loans Converted to Term	407	487
Income (loss) from continuing operations before income taxes	93,711	96,116
Current | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	5,484	8,152
Revolving Loans Converted to Term	52	66
Income (loss) from continuing operations before income taxes	5,536	8,218
30-59 days | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	512	734
Revolving Loans Converted to Term	13	21
Income (loss) from continuing operations before income taxes	525	755
30-59 days | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	61	79
Revolving Loans Converted to Term	6	11
Income (loss) from continuing operations before income taxes	67	90
60-89 days | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	308	451
Revolving Loans Converted to Term	9	13
Income (loss) from continuing operations before income taxes	317	464
60-89 days | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	33	47
Revolving Loans Converted to Term	4	11
Income (loss) from continuing operations before income taxes	37	58
Greater than 90 days | Domestic credit card: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	747	1,155
Revolving Loans Converted to Term	9	14
Income (loss) from continuing operations before income taxes	756	1,169
Greater than 90 days | International card businesses: | Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	64	76
Revolving Loans Converted to Term	4	10
Income (loss) from continuing operations before income taxes	$ 68	$ 86