Variable Interest Entity (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Total assets	$ 40,042.0	$ 35,889.0
Total liabilities	37,846.0	34,018.0
Variable Interest Entity, Primary Beneficiary [Member] | American Express Canada Credit Corporation Member [Member]
Variable Interest Entity [Line Items]
Total assets	0.4	466.0
Total liabilities	$ 0.0	$ 457.0