Regulatory Matters and Capital Adequacy (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Regulatory Matters And Capital Adequacy [Abstract]
Common Equity Tier 1 required, Well-capitalized ratios	6.50%
Common Equity Tier 1 Required, Basel III Standards 2019	7.00%
Common Equity Tier 1 required, Minimum capital ratio	4.50%
Risk-based capital required, Well-capitalized ratios	8.00%
Risk Based Capital Required, Basel III Standards 2019	8.50%
Risk-based capital required, Minimum capital ratios	6.00%
Well-capitalized ratios	10.00%
Basel III Standards 2019	10.50%
Minimum capital ratios	8.00%
Leverage capital required, Well-capitalized ratios	5.00%
Leverage Capital Required, Basel III Standards 2019	4.00%
Leverage capital required, Minimum capital ratios	4.00%
SLR, Basel III Standards 2019	3.00%
SLR, Minimum Capital Ratio	3.00%
Parent Company [Member] | American Express Company [Member]
Regulatory capital ratios
CET1 capital	$ 18,056	$ 17,498
Tier 1 capital	19,628	19,070
Total capital	$ 22,213	$ 21,653
CET1 capital ratio	10.70%	11.00%
Tier 1 capital ratio	11.60%	12.00%
Total capital ratio	13.20%	13.60%
Tier 1 leverage ratio	10.20%	10.40%
SLR ratio	8.80%	8.90%
Subsidiaries [Member] | American Express National Bank [Member]
Regulatory capital ratios
CET1 capital	$ 13,600	$ 11,564
Tier 1 capital	13,600	11,564
Total capital	$ 15,688	$ 13,574
CET1 capital ratio	13.40%	12.10%
Tier 1 capital ratio	13.40%	12.10%
Total capital ratio	15.40%	14.20%
Tier 1 leverage ratio	11.10%	9.90%
SLR ratio	9.30%	8.20%