Basis of Presentation (Policies)	9 Months Ended
Sep. 30, 2019
Derivative [Line Items]
Basis of Presentation	The preparation of Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and the disclosures of contingent assets and liabilities. These accounting estimates reflect the best judgment of management, but actual results could differ. Certain reclassifications of prior period amounts have been made to conform to the current period presentation.
Recently Adopted Accounting Standards	Recently Issued Accounting Standards In June 2016, the Financial Accounting Standards Board (FASB) issued new accounting guidance for the recognition of credit losses on financial instruments, effective January 1, 2020. The guidance introduces a new credit reserving methodology known as the Current Expected Credit Loss (CECL) methodology, which differs significantly from the incurred loss approach used today and will alter the estimation process, inputs and assumptions used in estimating credit losses. The CECL methodology requires measurement of expected credit losses for the estimated life of the financial instrument, not only based on historical experience and current conditions, but also by including reasonable and supportable forecasts incorporating forward-looking information. At the date of adoption, the change in reserves will be recorded in retained earnings as a cumulative-effect adjustment. We continue to evaluate the impact the new guidance will have on our financial position, results of operations and regulatory risk-based capital. As part of our evaluation of the estimated impacts of CECL, we have run multiple simulations based on our portfolio composition and current expectations of future economic conditions. The results of those preliminary simulations continue to indicate that our total reserves for credit losses related to our Card Member loans and receivables portfolios could have a net increase between 25 percent and 40 percent, with an increase in reserves of between 55 percent and 70 percent related to our Card Member loans portfolio and a decrease in reserves related to our Card Member receivables portfolio, all of which is based on the comparison of preliminary CECL estimates as compared to the incurred loss model applied today. The anticipated higher impact to our Card Member loans reserve is primarily driven by the longer average estimated loan life as compared to our Card Member receivables. The actual impact at adoption will depend on the outstanding balances, characteristics of our loan and receivable portfolios, macroeconomic conditions and forecasted information at the date of adoption. We are continuing our cross-functional implementation efforts and have substantially completed development of our CECL models. Model validation, user acceptance testing, and parallel runs will continue through the remainder of 2019. In addition, we continue to develop the business processes, policies and controls that satisfy the requirements of the new guidance. In addition, for available-for-sale debt securities, the new guidance prospectively replaces the other-than-temporary impairment model and requires the recognition of an allowance for reductions in a security’s fair value attributable to declines in credit quality, instead of a direct write-down of the security, when a valuation decline is determined to be other-than-temporary. We do not currently expect the impact of the new guidance on available-for-sale securities to be material at adoption. Recently Adopted Accounting Standards In February 2016, the FASB issued new accounting guidance on leases. The accounting standard, effective January 1, 2019, requires virtually all leases to be recognized on the Consolidated Balance Sheets. Effective January 1, 2019, we adopted the standard using the modified retrospective method, under which we elected the package of practical expedients and transition provisions allowing us to bring our existing operating leases onto the Consolidated Balance Sheet without adjusting comparative periods. Under the guidance we have also elected not to separate lease and non-lease components in recognition of the lease-related assets and liabilities, as well as the related lease expense.
Leases	We have operating leases for facilities and equipment, which are recorded as assets and liabilities for those leases with terms greater than 12 months. Lease-related assets, or right-of-use assets, are recognized at the lease commencement date at amounts equal to the respective lease liabilities, adjusted for prepaid lease payments, initial direct costs, and lease incentives received. Lease-related liabilities are recognized at the present value of the remaining contractual fixed lease payments, discounted using our incremental borrowing rate. Operating lease expense is recognized on a straight-line basis over the lease term, while variable lease payments are expensed as incurred.
Investments	Investment securities principally include available-for-sale debt securities carried at fair value on the Consolidated Balance Sheets, with unrealized gains and losses recorded in AOCI, net of income taxes. Realized gains and losses are recognized upon disposition of the securities using the specific identification method. Investment securities also include equity securities carried at fair value on the Consolidated Balance Sheets. The unrealized gains and losses on equity securities are recorded in the Consolidated Statements of Income.
Asset Securitizations	We periodically securitize Card Member loans and receivables arising from our card businesses through the transfer of those assets to securitization trusts, American Express Credit Account Master Trust (the Lending Trust) and American Express Issuance Trust II (the Charge Trust and together with the Lending Trust, the Trusts). The Trusts then issue debt securities collateralized by the transferred assets to third-party investors.The Trusts are considered VIEs as they have insufficient equity at risk to finance their activities, which are to issue debt securities that are collateralized by the underlying Card Member loans and receivables. We perform the servicing and key decision making for the Trusts, and therefore have the power to direct the activities that most significantly impact the Trusts’ economic performance, which are the collection of the underlying Card Member loans and receivables. In addition, we hold all of the variable interests in both Trusts, with the exception of the debt securities issued to third-party investors.
Asset Securitizations	These variable interests held by us provide us with the right to receive benefits and the obligation to absorb losses, which could be significant to both the Lending Trust and the Charge Trust. Based on these considerations, we are the primary beneficiary of the Trusts and therefore consolidate the Trusts.
Contingencies	We have accrued for certain of our outstanding legal proceedings. An accrual is recorded when it is both (a) probable that a loss has occurred and (b) the amount of loss can be reasonably estimated. There may be instances in which an exposure to loss exceeds the accrual. We evaluate, on a quarterly basis, developments in legal proceedings that could cause an increase or decrease in the amount of the accrual that has been previously recorded, or a revision to the disclosed estimated range of possible losses, as applicable.
Derivatives	We use derivative financial instruments to manage exposures to various market risks. These instruments derive their value from an underlying variable or multiple variables, including interest rates, foreign exchange rates, and an equity index or price, and are carried at fair value on the Consolidated Balance Sheets.
Fair Values	We have certain assets that are subject to measurement at fair value on a nonrecurring basis. For these assets, measurement at fair value in periods subsequent to their initial recognition is applicable if they are determined to be impaired or where there are observable price changes for equity investments without readily determinable fair values.
Guarantees	Our recognition of these instruments is at fair value. In addition, we establish reserves when a loss is probable and the amount can be reasonably estimated.
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivatives	The changes in the fair value of derivatives that are not designated as hedges are intended to offset the related foreign exchange gains or losses of the underlying foreign currency exposures.

Basis of Presentation (Policies)

9 Months Ended

Sep. 30, 2019

The preparation of Consolidated Financial Statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and the disclosures of contingent assets and liabilities. These accounting estimates reflect the best judgment of management, but actual results could differ.

Certain reclassifications of prior period amounts have been made to conform to the current period presentation.

Recently Adopted Accounting Standards

Recently Issued Accounting Standards

In June 2016, the Financial Accounting Standards Board (FASB) issued new accounting guidance for the recognition of credit losses on financial instruments, effective January 1, 2020. The guidance introduces a new credit reserving methodology known as the Current Expected Credit Loss (CECL) methodology, which differs significantly from the incurred loss approach used today and will alter the estimation process, inputs and assumptions used in estimating credit losses. The CECL methodology requires measurement of expected credit losses for the estimated life of the financial instrument, not only based on historical experience and current conditions, but also by including reasonable and supportable forecasts incorporating forward-looking information. At the date of adoption, the change in reserves will be recorded in retained earnings as a cumulative-effect adjustment.

We continue to evaluate the impact the new guidance will have on our financial position, results of operations and regulatory risk-based capital. As part of our evaluation of the estimated impacts of CECL, we have run multiple simulations based on our portfolio composition and current expectations of future economic conditions. The results of those preliminary simulations continue to indicate that our total reserves for credit losses related to our Card Member loans and receivables portfolios could have a net increase between 25 percent and 40 percent, with an increase in reserves of between 55 percent and 70 percent related to our Card Member loans portfolio and a decrease in reserves related to our Card Member receivables portfolio, all of which is based on the comparison of preliminary CECL estimates as compared to the incurred loss model applied today. The anticipated higher impact to our Card Member loans reserve is primarily driven by the longer average estimated loan life as compared to our Card Member receivables.

The actual impact at adoption will depend on the outstanding balances, characteristics of our loan and receivable portfolios, macroeconomic conditions and forecasted information at the date of adoption. We are continuing our cross-functional implementation efforts and have substantially completed development of our CECL models. Model validation, user acceptance testing, and parallel runs will continue through the remainder of 2019. In addition, we continue to develop the business processes, policies and controls that satisfy the requirements of the new guidance.

In addition, for available-for-sale debt securities, the new guidance prospectively replaces the other-than-temporary impairment model and requires the recognition of an allowance for reductions in a security’s fair value attributable to declines in credit quality, instead of a direct write-down of the security, when a valuation decline is determined to be other-than-temporary. We do not currently expect the impact of the new guidance on available-for-sale securities to be material at adoption.

Recently Adopted Accounting Standards

In February 2016, the FASB issued new accounting guidance on leases. The accounting standard, effective January 1, 2019, requires virtually all leases to be recognized on the Consolidated Balance Sheets. Effective January 1, 2019, we adopted the standard using the modified retrospective method, under which we elected the package of practical expedients and transition provisions allowing us to bring our existing operating leases onto the Consolidated Balance Sheet without adjusting comparative periods. Under the guidance we have also elected not to separate lease and non-lease components in recognition of the lease-related assets and liabilities, as well as the related lease expense.

Leases

We have operating leases for facilities and equipment, which are recorded as assets and liabilities for those leases with terms greater than 12 months. Lease-related assets, or right-of-use assets, are recognized at the lease commencement date at amounts equal to the respective lease liabilities, adjusted for prepaid lease payments, initial direct costs, and lease incentives received. Lease-related liabilities are recognized at the present value of the remaining contractual fixed lease payments, discounted using our incremental borrowing rate. Operating lease expense is recognized on a straight-line basis over the lease term, while variable lease payments are expensed as incurred.

Investments

Investment securities principally include available-for-sale debt securities carried at fair value on the Consolidated Balance Sheets, with unrealized gains and losses recorded in AOCI, net of income taxes. Realized gains and losses are recognized upon disposition of the securities using the specific identification method.

Investment securities also include equity securities carried at fair value on the Consolidated Balance Sheets. The unrealized gains and losses on equity securities are recorded in the Consolidated Statements of Income.

Asset Securitizations

We periodically securitize Card Member loans and receivables arising from our card businesses through the transfer of those assets to securitization trusts, American Express Credit Account Master Trust (the Lending Trust) and American Express Issuance Trust II (the Charge Trust and together with the Lending Trust, the Trusts). The Trusts then issue debt securities collateralized by the transferred assets to third-party investors.The Trusts are considered VIEs as they have insufficient equity at risk to finance their activities, which are to issue debt securities that are collateralized by the underlying Card Member loans and receivables. We perform the servicing and key decision making for the Trusts, and therefore have the power to direct the activities that most significantly impact the Trusts’ economic performance, which are the collection of the underlying Card Member loans and receivables. In addition, we hold all of the variable interests in both Trusts, with the exception of the debt securities issued to third-party investors.

Asset Securitizations

These variable interests held by us provide us with the right to receive benefits and the obligation to absorb losses, which could be significant to both the Lending Trust and the Charge Trust. Based on these considerations, we are the primary beneficiary of the Trusts and therefore consolidate the Trusts.

Contingencies

We have accrued for certain of our outstanding legal proceedings. An accrual is recorded when it is both (a) probable that a loss has occurred and (b) the amount of loss can be reasonably estimated. There may be instances in which an exposure to loss exceeds the accrual. We evaluate, on a quarterly basis, developments in legal proceedings that could cause an increase or decrease in the amount of the accrual that has been previously recorded, or a revision to the disclosed estimated range of possible losses, as applicable.

Derivatives

We use derivative financial instruments to manage exposures to various market risks. These instruments derive their value from an underlying variable or multiple variables, including interest rates, foreign exchange rates, and an equity index or price, and are carried at fair value on the Consolidated Balance Sheets.

Fair Values

We have certain assets that are subject to measurement at fair value on a nonrecurring basis. For these assets, measurement at fair value in periods subsequent to their initial recognition is applicable if they are determined to be impaired or where there are observable price changes for equity investments without readily determinable fair values.

Guarantees

Our recognition of these instruments is at fair value. In addition, we establish reserves when a loss is probable and the amount can be reasonably estimated.

Not Designated as Hedging Instrument [Member]

Derivative [Line Items]

Derivatives

The changes in the fair value of derivatives that are not designated as hedges are intended to offset the related foreign exchange gains or losses of the underlying foreign currency exposures.