Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2019
Policy (Text Block) [Abstract]
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. 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. 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. In conjunction with the adoption, we upgraded our lease administration software and updated our business processes and internal controls in support of the new guidance.
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. 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. 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.
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.

Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 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.

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.

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.

In conjunction with the adoption, we upgraded our lease administration software and updated our business processes and internal controls in support of the new guidance.

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.

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.

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.

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.

- Definition

Disclosure of accounting policy for investments in financial assets, including marketable securities (debt and equity securities with readily determinable fair values), investments accounted for under the equity method and cost method, securities borrowed and loaned, and repurchase and resale agreements. For marketable securities, the disclosure may include the entity's accounting treatment for transfers between investment categories and how the fair values for such securities are determined. Also, for all investments, an entity may describe its policy for assessing, recognizing and measuring impairment of the investment.

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- Definition

Disclosure of accounting policy for transfers and servicing financial assets, including securitization transactions as well as repurchase and resale agreements. This disclosure may include how the entity (1) determines whether a transaction is accounted for as a sale; (2) accounts for a sale transaction, including the initial and subsequent accounting for any interests that the entity obtains or continues to hold in the transaction, how such interests are valued, and the significant assumptions used in the valuation; (3) accounts for a transaction that does not qualify for sale treatment (that is, a financing); and (4) accounts for its servicing assets and liabilities ("servicing"), including how such servicing is measured initially and subsequently, and the methodology and significant assumptions used to value such servicing.

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