Asset Securitizations (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Assets from Trusts [Line Items]
Restricted cash included in Other assets per Consolidated Balance Sheets	$ 1,032	$ 337	$ 2,087	$ 286
Variable Interest Entity
Assets from Trusts [Line Items]
Restricted cash included in Other assets per Consolidated Balance Sheets	783	62
American Express Charge Trust [Member] | Variable Interest Entity
Assets from Trusts [Line Items]
Restricted cash included in Other assets per Consolidated Balance Sheets	0	7
American Express Lending Trust [Member] | Variable Interest Entity
Assets from Trusts [Line Items]
Restricted cash included in Other assets per Consolidated Balance Sheets	$ 783	$ 55