Variable Interest Entity (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Total assets	$ 39,071	$ 35,889
Total liabilities	37,061	34,018
Variable Interest Entity, Primary Beneficiary [Member] | American Express Canada Credit Corporation Member [Member]
Variable Interest Entity [Line Items]
Total assets	8	466
Total liabilities	0	457
Liabilities eliminated in consolidation	0	0
Assets eliminated in consolidation	$ 0	$ 0