Variable Interest Entity (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total assets	$ 35,889	$ 31,936
Total liabilities	34,018	29,727
Variable Interest Entity, Primary Beneficiary [Member] | American Express Canada Credit Corporation Member [Member]
Variable Interest Entity [Line Items]
Total assets	500	1,700
Total liabilities	500	1,700
Liabilities eliminated in consolidation	0	1,300
Assets eliminated in consolidation	$ 0	$ 1,700