Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2017
Summary Of Significant Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The Consolidated Financial Statements of Credco are prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). Significant intercompany transactions are eliminated. Credco consolidates entities in which it holds a controlling financial interest. For voting interest entities, Credco is considered to hold a controlling financial interest when it is able to exercise control over the investees’ operating and financial decisions. For variable interest entities (VIEs), the determination of which is based on the amount and characteristics of the entity’s equity, Credco is considered to hold a controlling financial interest when it is determined to be the primary beneficiary. A primary beneficiary is the party that has both: (1) the power to direct the activities that most significantly impact that VIE’s economic performance, and (2) the obligation to absorb the losses of, or the right to receive the benefits from, the VIE that could potentially be significant to that VIE.
Foreign Currency	Foreign Currency Monetary assets and liabilities denominated in foreign currencies are translated into U.S. dollars based upon exchange rates prevailing at the end of the reporting period; non-monetary assets and liabilities are translated at the historic exchange rate at the date of the transaction; revenues and expenses are translated at the average month-end exchange rates during the year. Resulting translation adjustments, along with any related qualifying hedge and tax effects, are included in accumulated other comprehensive income (loss) (AOCI), a component of shareholder’s equity. Translation adjustments, including qualifying hedge and tax effects, are reclassified to earnings upon the sale or substantial liquidation of investments in foreign operations. Gains and losses related to transactions in a currency other than the functional currency are reported net in Other expenses, in Credco’s Consolidated Statements of Income.
Amounts Based on Estimates and Assumptions	Amounts Based on Estimates and Assumptions Accounting estimates are an integral part of the Consolidated Financial Statements. These estimates are based, in part, on management’s assumptions concerning future events. Among the more significant assumptions are those that relate to reserves for Card Member losses on receivables and loans, fair value measurements and income taxes. These accounting estimates reflect the best judgment of management, but actual results could differ.
Revenues and Expenses	Discount Revenue Earned from Purchased Card Member Receivables and Loans Credco earns discount revenue from purchasing Card Member receivables and loans at a discount to par value. The discount is deferred and recognized as revenue over the period that the receivables and loans are estimated to be outstanding or funded. Estimates are based on the historical average life of Card Member receivables and loans. Interest Income from Affiliates Interest income from affiliates is earned on interest-bearing loans made by Credco to affiliates. Interest income is accrued primarily using the average daily balance method on loans and is recognized based on the outstanding loan principal amount and interest rates specified in the agreements until the outstanding loan balance is paid. Finance Revenue Finance revenue is assessed using the average daily balance method for Card Member loans and is recognized based upon the loan principal amount outstanding in accordance with the terms of the applicable account agreement until the outstanding balance is paid or written off. Interest Expense Interest expense includes interest incurred primarily to fund Card Member receivables and loans, general corporate purposes and liquidity needs, and is recognized as incurred.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash and amounts due from banks, interest-bearing bank balances, and other highly liquid investments with original maturities of 90 days or less.
Accounts Receivable And Loans and Reserves For Cardmember Losses [Abstract]
Card Member receivables and loans	Card Member Receivables Card Member receivables represent amounts due on American Express charge card products. For American Express, the Card Member receivables are recorded at the time a Card Member enters into a point-of-sale transaction with a merchant. Each charge card transaction is authorized based on its likely economics, a Card Member’s most recent credit information and spend patterns. Additionally, global spend limits are established to limit the maximum exposure for American Express. Charge Card Members generally must pay the full amount billed each month. Credco records these Card Member receivables at the time they are purchased from TRS and certain of its subsidiaries that issue the card (card issuers). Card Member receivable balances are presented on the Consolidated Balance Sheets, net of reserves for losses (refer to Note 3). Card Member Loans Card Member loans represent revolving amounts due on American Express cards. For American Express lending card products, these Card Member loans are recorded at the time a Card Member enters into a point-of-sale transaction with a merchant, as well as amounts due from charge Card Members who utilize the Pay Over Time features on their account and elect to revolve a portion of the outstanding balance by entering into a revolving payment arrangement with American Express. These loans have a range of terms such as credit limits, interest rates, fees and payment structures, which can be revised over time based on new information about Card Members and in accordance with applicable regulations and the respective product’s terms and conditions. Card Members holding revolving loans are typically required to make monthly payments based on pre-established amounts and the amounts that Card Members choose to revolve are subject to finance charges. Credco records these Card Member loans at the time they are purchased from TRS and certain of its subsidiaries that issue the card (card issuers). Card Member loans are presented on the Consolidated Balance Sheets, net of reserves for losses (refer to Note 3), and include principal and any related accrued interest and fees. American Express’ policy generally is to cease accruing interest on a Card Member loan at the time the account is written off, and establish reserves for interest that will not be collected.
Reserves For Losses Policy [Abstract]
Reserves for losses	Reserves for losses relating to Card Member receivables and loans represent management’s best estimate of the probable inherent losses in Credco’s outstanding portfolio of receivables and loans, as of the balance sheet date. Management’s evaluation process requires certain estimates and judgments. Reserves for losses are primarily based upon statistical and analytical models that analyze portfolio performance and reflect management’s judgment regarding the quantitative components of the reserve. The models take into account several factors, including delinquency-based loss migration rates, loss emergence periods and average losses and recoveries over an appropriate historical period. Management considers whether to adjust the quantitative reserves for certain external and internal qualitative factors, which may increase or decrease the reserves for losses on Card Member receivables and loans. These external factors include employment, spend, sentiment, housing and credit, and changes in the legal and regulatory environment, while the internal factors include increased risk in certain portfolios, impact of risk management initiatives, changes in underwriting requirements and overall process stability. As part of this evaluation process, management also considers various reserve coverage metrics, such as reserves as a percentage of past due amounts, reserves as a percentage of Card Member receivables or loans and net write-off coverage ratios. Card Member receivables and loans balances are written off when management considers amounts to be uncollectible, which is generally determined by the number of days past due and is typically no later than 180 days past due. Card Member receivables and loans in bankruptcy or owed by deceased individuals are generally written off upon notification, and recoveries are recognized as they are collected.
Derivatives And Hedging Activities Policy [Abstract]
Derivatives Financial Instruments and Hedging Activities	Credco’s derivatives are carried at fair value on the Consolidated Balance Sheets. The accounting for changes in fair value depends on the instruments’ intended use and the resulting hedge designation, if any, as discussed below. Credco formally assesses, at inception of the hedge accounting relationship and on a quarterly basis, whether derivatives designated as hedges are highly effective in offsetting the fair value or cash flows of the hedged items. These assessments usually are made through the application of a regression analysis method. If it is determined that a derivative is not highly effective as a hedge, Credco will discontinue the application of hedge accounting. To the extent the fair value hedge is effective, the gain or loss on the hedging instrument offsets the loss or gain on the hedged item attributable to the hedged risk. Any difference between the changes in the fair value of the derivative and the changes in the hedged item is referred to as hedge ineffectiveness and is reported as a component of Other expenses. Credco primarily designates foreign currency derivatives, typically foreign exchange forwards, and on occasion foreign currency denominated debt, as hedges of net investments in certain foreign operations. Credco has derivatives that act as economic hedges, but are not designated as such for hedge accounting purposes. Foreign currency transactions from time to time may be partially or fully economically hedged through foreign currency contracts, primarily foreign exchange forwards. These hedges generally mature within one year. Foreign currency contracts involve the purchase and sale of designated currencies at an agreed upon rate for settlement on a specified date. 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.
Fair Values [Abstract]
Fair Value Measurements	Credco monitors the market conditions and evaluates the fair value hierarchy levels at least quarterly. For any transfers in and out of the levels of the fair value hierarchy, Credco discloses the fair value measurement at the beginning of the reporting period during which the transfer occurred.
Income Tax Policy [Abstract]
Income taxes	The Tax Act, enacted by the U.S. government on December 22, 2017, makes broad and complex changes to the U.S. tax code which will require time to interpret. The SEC issued Staff Accounting Bulletin No. 118 (SAB 118) in December, 2017, to provide guidance on accounting for the effects of the Tax Act. SAB 118 provides for a measurement period of up to one year from the Tax Act enactment date for companies to complete their assessment of and accounting for those effects of the Tax Act required under ASC 740 “Implementation Guidance on Accounting for Uncertainty in Income Taxes’’ to be reported in the period of enactment. Under SAB 118, a company must first reflect the income tax effects of the Tax Act for which the accounting is complete in the period of the date of enactment. To the extent the accounting for other income tax effects is incomplete, but for which a reasonable estimate can be determined, companies must record a provisional estimate to be included in their financial statements. For any income tax effect for which a reasonable estimate cannot be determined, an entity must continue to apply ASC 740 based on the provisions of the tax laws in effect immediately prior to the Tax Act being enacted until such time as a reasonable estimate can be determined. Credco records a deferred income tax (benefit) provision when there are differences between assets and liabilities measured for financial reporting and for income tax return purposes. These temporary differences result in taxable or deductible amounts in future years and are measured using the tax rates and laws that will be in effect when such differences are expected to reverse. In particular, the 2017 balances were reduced to reflect the remeasurement of certain federal net deferred tax assets due to the enacted lower federal tax rate of 21 percent. Interest and penalties relating to unrecognized tax benefits are reported in the income tax provision.
Income tax uncertainties	The amount of benefit recognized for financial reporting purposes is based on management’s best judgment of the largest amount of benefit that is more likely than not to be realized on ultimate settlement with the taxing authority given the facts, circumstances and information available at the reporting date. Credco adjusts the level of unrecognized tax benefits when there is new information available to assess the likelihood of the outcome.

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Summary Of Significant Accounting Policies [Abstract]

The Consolidated Financial Statements of Credco are prepared in conformity with accounting principles generally accepted in the United States of America (GAAP). Significant intercompany transactions are eliminated.

Credco consolidates entities in which it holds a controlling financial interest. For voting interest entities, Credco is considered to hold a controlling financial interest when it is able to exercise control over the investees’ operating and financial decisions. For variable interest entities (VIEs), the determination of which is based on the amount and characteristics of the entity’s equity, Credco is considered to hold a controlling financial interest when it is determined to be the primary beneficiary. A primary beneficiary is the party that has both: (1) the power to direct the activities that most significantly impact that VIE’s economic performance, and (2) the obligation to absorb the losses of, or the right to receive the benefits from, the VIE that could potentially be significant to that VIE.

Foreign Currency

Monetary assets and liabilities denominated in foreign currencies are translated into U.S. dollars based upon exchange rates prevailing at the end of the reporting period; non-monetary assets and liabilities are translated at the historic exchange rate at the date of the transaction; revenues and expenses are translated at the average month-end exchange rates during the year. Resulting translation adjustments, along with any related qualifying hedge and tax effects, are included in accumulated other comprehensive income (loss) (AOCI), a component of shareholder’s equity. Translation adjustments, including qualifying hedge and tax effects, are reclassified to earnings upon the sale or substantial liquidation of investments in foreign operations. Gains and losses related to transactions in a currency other than the functional currency are reported net in Other expenses, in Credco’s Consolidated Statements of Income.

Amounts Based on Estimates and Assumptions

Accounting estimates are an integral part of the Consolidated Financial Statements. These estimates are based, in part, on management’s assumptions concerning future events. Among the more significant assumptions are those that relate to reserves for Card Member losses on receivables and loans, fair value measurements and income taxes. These accounting estimates reflect the best judgment of management, but actual results could differ.

Revenues and Expenses

Discount Revenue Earned from Purchased Card Member Receivables and Loans

Credco earns discount revenue from purchasing Card Member receivables and loans at a discount to par value. The discount is deferred and recognized as revenue over the period that the receivables and loans are estimated to be outstanding or funded. Estimates are based on the historical average life of Card Member receivables and loans.

Interest Income from Affiliates

Interest income from affiliates is earned on interest-bearing loans made by Credco to affiliates. Interest income is accrued primarily using the average daily balance method on loans and is recognized based on the outstanding loan principal amount and interest rates specified in the agreements until the outstanding loan balance is paid.

Finance Revenue

Finance revenue is assessed using the average daily balance method for Card Member loans and is recognized based upon the loan principal amount outstanding in accordance with the terms of the applicable account agreement until the outstanding balance is paid or written off.

Interest Expense

Interest expense includes interest incurred primarily to fund Card Member receivables and loans, general corporate purposes and liquidity needs, and is recognized as incurred.

Cash and Cash Equivalents

Cash and cash equivalents include cash and amounts due from banks, interest-bearing bank balances, and other highly liquid investments with original maturities of 90 days or less.

Accounts Receivable And Loans and Reserves For Cardmember Losses [Abstract]

Card Member receivables and loans

Card Member Receivables

Card Member receivables represent amounts due on American Express charge card products. For American Express, the Card Member receivables are recorded at the time a Card Member enters into a point-of-sale transaction with a merchant. Each charge card transaction is authorized based on its likely economics, a Card Member’s most recent credit information and spend patterns. Additionally, global spend limits are established to limit the maximum exposure for American Express. Charge Card Members generally must pay the full amount billed each month.

Credco records these Card Member receivables at the time they are purchased from TRS and certain of its subsidiaries that issue the card (card issuers). Card Member receivable balances are presented on the Consolidated Balance Sheets, net of reserves for losses (refer to Note 3).

Card Member Loans

Card Member loans represent revolving amounts due on American Express cards. For American Express lending card products, these Card Member loans are recorded at the time a Card Member enters into a point-of-sale transaction with a merchant, as well as amounts due from charge Card Members who utilize the Pay Over Time features on their account and elect to revolve a portion of the outstanding balance by entering into a revolving payment arrangement with American Express. These loans have a range of terms such as credit limits, interest rates, fees and payment structures, which can be revised over time based on new information about Card Members and in accordance with applicable regulations and the respective product’s terms and conditions. Card Members holding revolving loans are typically required to make monthly payments based on pre-established amounts and the amounts that Card Members choose to revolve are subject to finance charges.

Credco records these Card Member loans at the time they are purchased from TRS and certain of its subsidiaries that issue the card (card issuers). Card Member loans are presented on the Consolidated Balance Sheets, net of reserves for losses (refer to Note 3), and include principal and any related accrued interest and fees. American Express’ policy generally is to cease accruing interest on a Card Member loan at the time the account is written off, and establish reserves for interest that will not be collected.

Reserves For Losses Policy [Abstract]

Reserves for losses

Reserves for losses relating to Card Member receivables and loans represent management’s best estimate of the probable inherent losses in Credco’s outstanding portfolio of receivables and loans, as of the balance sheet date. Management’s evaluation process requires certain estimates and judgments.

Reserves for losses are primarily based upon statistical and analytical models that analyze portfolio performance and reflect management’s judgment regarding the quantitative components of the reserve. The models take into account several factors, including delinquency-based loss migration rates, loss emergence periods and average losses and recoveries over an appropriate historical period. Management considers whether to adjust the quantitative reserves for certain external and internal qualitative factors, which may increase or decrease the reserves for losses on Card Member receivables and loans. These external factors include employment, spend, sentiment, housing and credit, and changes in the legal and regulatory environment, while the internal factors include increased risk in certain portfolios, impact of risk management initiatives, changes in underwriting requirements and overall process stability. As part of this evaluation process, management also considers various reserve coverage metrics, such as reserves as a percentage of past due amounts, reserves as a percentage of Card Member receivables or loans and net write-off coverage ratios.

Card Member receivables and loans balances are written off when management considers amounts to be uncollectible, which is generally determined by the number of days past due and is typically no later than 180 days past due. Card Member receivables and loans in bankruptcy or owed by deceased individuals are generally written off upon notification, and recoveries are recognized as they are collected.

Derivatives And Hedging Activities Policy [Abstract]

Derivatives Financial Instruments and Hedging Activities

Credco’s derivatives are carried at fair value on the Consolidated Balance Sheets. The accounting for changes in fair value depends on the instruments’ intended use and the resulting hedge designation, if any, as discussed below.

Credco formally assesses, at inception of the hedge accounting relationship and on a quarterly basis, whether derivatives designated as hedges are highly effective in offsetting the fair value or cash flows of the hedged items. These assessments usually are made through the application of a regression analysis method. If it is determined that a derivative is not highly effective as a hedge, Credco will discontinue the application of hedge accounting.

To the extent the fair value hedge is effective, the gain or loss on the hedging instrument offsets the loss or gain on the hedged item attributable to the hedged risk. Any difference between the changes in the fair value of the derivative and the changes in the hedged item is referred to as hedge ineffectiveness and is reported as a component of Other expenses.

Credco primarily designates foreign currency derivatives, typically foreign exchange forwards, and on occasion foreign currency denominated debt, as hedges of net investments in certain foreign operations.

Credco has derivatives that act as economic hedges, but are not designated as such for hedge accounting purposes. Foreign currency transactions from time to time may be partially or fully economically hedged through foreign currency contracts, primarily foreign exchange forwards. These hedges generally mature within one year. Foreign currency contracts involve the purchase and sale of designated currencies at an agreed upon rate for settlement on a specified date.

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.

Fair Values [Abstract]

Fair Value Measurements

Credco monitors the market conditions and evaluates the fair value hierarchy levels at least quarterly. For any transfers in and out of the levels of the fair value hierarchy, Credco discloses the fair value measurement at the beginning of the reporting period during which the transfer occurred.

Income Tax Policy [Abstract]

Income taxes

The Tax Act, enacted by the U.S. government on December 22, 2017, makes broad and complex changes to the U.S. tax code which will require time to interpret. The SEC issued Staff Accounting Bulletin No. 118 (SAB 118) in December, 2017, to provide guidance on accounting for the effects of the Tax Act. SAB 118 provides for a measurement period of up to one year from the Tax Act enactment date for companies to complete their assessment of and accounting for those effects of the Tax Act required under ASC 740 “Implementation Guidance on Accounting for Uncertainty in Income Taxes’’ to be reported in the period of enactment. Under SAB 118, a company must first reflect the income tax effects of the Tax Act for which the accounting is complete in the period of the date of enactment. To the extent the accounting for other income tax effects is incomplete, but for which a reasonable estimate can be determined, companies must record a provisional estimate to be included in their financial statements. For any income tax effect for which a reasonable estimate cannot be determined, an entity must continue to apply ASC 740 based on the provisions of the tax laws in effect immediately prior to the Tax Act being enacted until such time as a reasonable estimate can be determined.

Credco records a deferred income tax (benefit) provision when there are differences between assets and liabilities measured for financial reporting and for income tax return purposes. These temporary differences result in taxable or deductible amounts in future years and are measured using the tax rates and laws that will be in effect when such differences are expected to reverse. In particular, the 2017 balances were reduced to reflect the remeasurement of certain federal net deferred tax assets due to the enacted lower federal tax rate of 21 percent.

Interest and penalties relating to unrecognized tax benefits are reported in the income tax provision.

Income tax uncertainties

The amount of benefit recognized for financial reporting purposes is based on management’s best judgment of the largest amount of benefit that is more likely than not to be realized on ultimate settlement with the taxing authority given the facts, circumstances and information available at the reporting date. Credco adjusts the level of unrecognized tax benefits when there is new information available to assess the likelihood of the outcome.