Basis of Presentation and Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation [Policy Text Block]	Basis of Presentation The interim consolidated financial statements include the accounts of The Travelers Companies, Inc. (together with its subsidiaries, the Company). These financial statements are prepared in conformity with U.S. generally accepted accounting principles (GAAP) and are unaudited. In the opinion of the Company’s management, all adjustments necessary for a fair presentation have been reflected. Certain financial information that is normally included in annual financial statements prepared in accordance with GAAP, but that is not required for interim reporting purposes, has been omitted. All material intercompany transactions and balances have been eliminated. The accompanying interim consolidated financial statements and related notes should be read in conjunction with the Company’s consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 (the Company’s 2019 Annual Report). The preparation of the interim consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the interim consolidated financial statements and the reported amounts of revenues and claims and expenses during the reporting period. Actual results could differ from those estimates. Certain reclassifications have been made to the 2019 financial statements to conform to the 2020 presentation.
Adoption of Accounting Standards [Policy Text Block]	Adoption of Accounting Standards Registered Debt Offerings that Include Credit Enhancements from an Affiliate In March 2020, the Securities and Exchange Commission (SEC) adopted amendments to the financial disclosure requirements related to certain debt securities, including registered debt securities issued by a wholly-owned, operating subsidiary that are fully and unconditionally guaranteed by the parent company. Prior to the amendments, a parent guarantor was required to provide condensed consolidating financial information for so long as the guaranteed securities were outstanding, regardless of whether the subsidiary issuer could have suspended its public reporting obligations under the applicable SEC requirements with respect to the securities. In accordance with the amended requirements, a parent guarantor may cease providing the condensed consolidating financial information if the corresponding subsidiary issuer’s public reporting obligation is suspended. The amendments to the financial disclosure requirements are effective on January 4, 2021; however, the SEC permits voluntary compliance in advance of the effective date. The Company elected to apply the amended requirements for the quarter ended March 31, 2020, and is no longer providing condensed consolidating financial information that resulted from the registered debt obligations of its subsidiaries, Travelers Property Casualty Corp. and Travelers Insurance Group Holdings Inc., that were disclosed in note 8 of the financial statements in the Company’s 2019 Annual Report. Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments In June 2016, the Financial Accounting Standards Board issued updated guidance for the accounting for credit losses for financial instruments. The updated guidance applies a new credit loss model (current expected credit losses or CECL) for determining credit-related impairments for financial instruments measured at amortized cost (including reinsurance recoverables and structured settlements that are recorded as part of reinsurance recoverables) and requires an entity to estimate the credit losses expected over the life of an exposure or pool of exposures. The estimate of expected credit losses should consider historical information, current information, as well as reasonable and supportable forecasts, including estimates of prepayments. The expected credit losses, and subsequent adjustments to such losses, are recorded through an allowance account that is deducted from the amortized cost basis of the financial asset, with the net carrying value of the financial asset presented on the consolidated balance sheet at the amount expected to be collected. The updated guidance also amends the previous other-than-temporary impairment model for available-for-sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limits the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists. The Company adopted the updated guidance for the quarter ending March 31, 2020. For available-for-sale debt securities, the updated guidance was applied prospectively. For financial instruments measured at amortized cost, the updated guidance was applied by a cumulative effect adjustment to the opening balance of retained earnings as of January 1, 2020, the beginning of the period of adoption. The adoption of this guidance resulted in the recognition of an after-tax cumulative effect adjustment of $43 million to reflect the impact of recognizing expected credit losses, as compared to incurred credit losses recognized under the previous guidance. This adjustment is primarily associated with structured settlements that are recorded as part of reinsurance recoverables. The cumulative effect adjustment decreased retained earnings as of January 1, 2020 and increased the allowance for estimated uncollectible reinsurance. For additional information regarding accounting standards that the Company adopted during the periods presented, see note 1 of notes to the consolidated financial statements in the Company’s 2019 Annual Report.
Investment Impairments [Policy Text Block]	Investment Impairments The Company conducts a periodic review to identify and evaluate invested assets that may have credit impairments. Credit Impairments of Fixed Maturities Some of the factors considered in assessing impairment of fixed maturities due to credit-related factors include: (1) the extent to which the fair value has been less than amortized cost; (2) the financial condition, near-term and long-term prospects for the issuer, including the relevant industry conditions and trends, and implications of rating agency actions and offering prices; (3) the likelihood of the recoverability of principal and interest; and (4) whether it is more likely than not that the Company will be required to sell the investment prior to an anticipated recovery in value. Beginning on January 1, 2020, credit losses are recognized through an allowance account. See note 1 - Adoption of Accounting Standards - Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments for additional information. For fixed maturity investments that the Company does not intend to sell or for which it is more likely than not that the Company would not be required to sell before an anticipated recovery in value, the Company separates the credit loss component of the impairment from the amount related to all other factors and reports the credit loss component in net realized investment gains (losses). The impairment related to all other factors (non-credit factors) is reported in other comprehensive income. The allowance is adjusted for any additional credit losses and subsequent recoveries. Upon recognizing a credit loss, the cost basis is not adjusted. For fixed maturities where the Company records a credit loss, a determination is made as to the cause of the impairment and whether the Company expects a recovery in the value. For fixed maturities where the Company expects a recovery in value, the constant effective yield method is utilized, and the investment is amortized to par. For fixed maturity investments the Company intends to sell or for which it is more likely than not that the Company will be required to sell before an anticipated recovery in value, the full amount of the impairment is included in net realized investment gains (losses). The new cost basis of the investment is the previous amortized cost basis less the impairment recognized in net realized investment gains (losses). The new cost basis is not adjusted for any subsequent recoveries in fair value. The Company reports investment income accrued separately from fixed maturities, available for sale, and has elected not to measure an allowance for credit losses for investment income accrued. Investment income accrued is written off through net realized investment gains (losses) at the time the issuer of the bond defaults or is expected to default on payments. Uncollectible available-for-sale debt securities are written-off when the Company determines that no additional payments of principle or interest will be received.
Reinsurance Recoverables [Policy Text Block]	Reinsurance Recoverables Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. Included in reinsurance recoverables are amounts related to certain structured settlements. The Company reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance. The allowance is based upon the Company’s ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. For structured settlements, the allowance is also based upon the Company’s ongoing review of life insurers’ creditworthiness and estimated amounts of coverage that would be available from state guaranty funds if a life insurer defaults. A probability-of-default methodology which reflects current and forecasted economic conditions is used to estimate the amount of uncollectible reinsurance due to credit-related factors and the estimate is reported in an allowance for estimated uncollectible reinsurance. The allowance also includes estimated uncollectible amounts related to dispute risk with reinsurers. Amounts deemed to be uncollectible, including amounts due from known insolvent reinsurers, are written off against the allowance. Changes in the allowance, as well as any subsequent collections of amounts previously written off, are reported as part of claims and claim adjustment expenses. The Company evaluates and monitors the financial condition of its reinsurers under voluntary reinsurance arrangements to minimize its exposure to significant losses from reinsurer insolvencies.
Contractholder Receivables and Payables [Policy Text Block]	Contractholder Receivables and Payables Under certain workers’ compensation insurance contracts with deductible features, the Company is obligated to pay the claimant for the full amount of the claim. The Company is subsequently reimbursed by the policyholder for the deductible amount. These amounts are included on a gross basis in the consolidated balance sheet in both contractholder payables and contractholder receivables. Contractholder receivables are reported net of an allowance for expected credit losses. The allowance is based upon the Company’s ongoing review of amounts outstanding, changes in policyholder credit standing, and other relevant factors. A probability-of-default methodology which reflects current and forecasted economic conditions is used to estimate the allowance for expected credit losses.
Premiums and Unearned Premium Reserves [Policy Text Block]	Premiums and Unearned Premium Reserves Premiums are recognized as revenues pro rata over the policy period. Unearned premium reserves represent the unexpired portion of policy premiums. Accrued retrospective premiums are included in premium balances receivable. Premium balances receivable are reported net of an allowance for expected credit losses. The allowance is based upon the Company’s ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by the Company’s ability to cancel the policy if the policyholder does not pay the premium.

Basis of Presentation and Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Presentation [Policy Text Block]

Basis of Presentation

The interim consolidated financial statements include the accounts of The Travelers Companies, Inc. (together with its subsidiaries, the Company). These financial statements are prepared in conformity with U.S. generally accepted accounting principles (GAAP) and are unaudited. In the opinion of the Company’s management, all adjustments necessary for a fair presentation have been reflected. Certain financial information that is normally included in annual financial statements prepared in accordance with GAAP, but that is not required for interim reporting purposes, has been omitted. All material intercompany transactions and balances have been eliminated. The accompanying interim consolidated financial statements and related notes should be read in conjunction with the Company’s consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 (the Company’s 2019 Annual Report).

The preparation of the interim consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the interim consolidated financial statements and the reported amounts of revenues and claims and expenses during the reporting period. Actual results could differ from those estimates. Certain reclassifications have been made to the 2019 financial statements to conform to the 2020 presentation.

Adoption of Accounting Standards [Policy Text Block]

Adoption of Accounting Standards

Registered Debt Offerings that Include Credit Enhancements from an Affiliate

In March 2020, the Securities and Exchange Commission (SEC) adopted amendments to the financial disclosure requirements related to certain debt securities, including registered debt securities issued by a wholly-owned, operating subsidiary that are fully and unconditionally guaranteed by the parent company. Prior to the amendments, a parent guarantor was required to provide condensed consolidating financial information for so long as the guaranteed securities were outstanding, regardless of whether the subsidiary issuer could have suspended its public reporting obligations under the applicable SEC requirements with respect to the securities. In accordance with the amended requirements, a parent guarantor may cease providing the condensed consolidating financial information if the corresponding subsidiary issuer’s public reporting obligation is suspended. The amendments to the financial disclosure requirements are effective on January 4, 2021; however, the SEC permits voluntary compliance in advance of the effective date. The Company elected to apply the amended requirements for the quarter ended March 31, 2020, and is no longer providing condensed consolidating financial information that resulted from the registered debt obligations of its subsidiaries, Travelers Property Casualty Corp. and Travelers Insurance Group Holdings Inc., that were disclosed in note 8 of the financial statements in the Company’s 2019 Annual Report.

Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments

In June 2016, the Financial Accounting Standards Board issued updated guidance for the accounting for credit losses for financial instruments. The updated guidance applies a new credit loss model (current expected credit losses or CECL) for determining credit-related impairments for financial instruments measured at amortized cost (including reinsurance recoverables and structured settlements that are recorded as part of reinsurance recoverables) and requires an entity to estimate the credit losses expected over the life of an exposure or pool of exposures. The estimate of expected credit losses should consider historical information, current information, as well as reasonable and supportable forecasts, including estimates of prepayments. The expected credit losses, and subsequent adjustments to such losses, are recorded through an allowance account that is deducted from the amortized cost basis of the financial asset, with the net carrying value of the financial asset presented on the consolidated balance sheet at the amount expected to be collected.

The updated guidance also amends the previous other-than-temporary impairment model for available-for-sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limits the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists.

The Company adopted the updated guidance for the quarter ending March 31, 2020. For available-for-sale debt securities, the updated guidance was applied prospectively. For financial instruments measured at amortized cost, the updated guidance was

applied by a cumulative effect adjustment to the opening balance of retained earnings as of January 1, 2020, the beginning of the period of adoption. The adoption of this guidance resulted in the recognition of an after-tax cumulative effect adjustment of $43 million to reflect the impact of recognizing expected credit losses, as compared to incurred credit losses recognized under the previous guidance. This adjustment is primarily associated with structured settlements that are recorded as part of reinsurance recoverables. The cumulative effect adjustment decreased retained earnings as of January 1, 2020 and increased the allowance for estimated uncollectible reinsurance.

For additional information regarding accounting standards that the Company adopted during the periods presented, see note 1 of notes to the consolidated financial statements in the Company’s 2019 Annual Report.

Investment Impairments [Policy Text Block]

Investment Impairments

The Company conducts a periodic review to identify and evaluate invested assets that may have credit impairments.

Credit Impairments of Fixed Maturities

Some of the factors considered in assessing impairment of fixed maturities due to credit-related factors include: (1) the extent to which the fair value has been less than amortized cost; (2) the financial condition, near-term and long-term prospects for the issuer, including the relevant industry conditions and trends, and implications of rating agency actions and offering prices; (3) the likelihood of the recoverability of principal and interest; and (4) whether it is more likely than not that the Company will be required to sell the investment prior to an anticipated recovery in value.

Beginning on January 1, 2020, credit losses are recognized through an allowance account. See note 1 - Adoption of Accounting Standards - Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments for additional information.

For fixed maturity investments that the Company does not intend to sell or for which it is more likely than not that the Company would not be required to sell before an anticipated recovery in value, the Company separates the credit loss component of the impairment from the amount related to all other factors and reports the credit loss component in net realized investment gains (losses). The impairment related to all other factors (non-credit factors) is reported in other comprehensive income. The allowance is adjusted for any additional credit losses and subsequent recoveries. Upon recognizing a credit loss, the cost basis is not adjusted.

For fixed maturities where the Company records a credit loss, a determination is made as to the cause of the impairment and whether the Company expects a recovery in the value. For fixed maturities where the Company expects a recovery in value, the constant effective yield method is utilized, and the investment is amortized to par.

For fixed maturity investments the Company intends to sell or for which it is more likely than not that the Company will be required to sell before an anticipated recovery in value, the full amount of the impairment is included in net realized investment gains (losses). The new cost basis of the investment is the previous amortized cost basis less the impairment recognized in net realized investment gains (losses). The new cost basis is not adjusted for any subsequent recoveries in fair value.

The Company reports investment income accrued separately from fixed maturities, available for sale, and has elected not to measure an allowance for credit losses for investment income accrued. Investment income accrued is written off through net realized investment gains (losses) at the time the issuer of the bond defaults or is expected to default on payments.

Uncollectible available-for-sale debt securities are written-off when the Company determines that no additional payments of principle or interest will be received.

Reinsurance Recoverables [Policy Text Block]

Reinsurance Recoverables

Amounts recoverable from reinsurers are estimated in a manner consistent with the associated claim liability. Included in reinsurance recoverables are amounts related to certain structured settlements. The Company reports its reinsurance recoverables net of an allowance for estimated uncollectible reinsurance. The allowance is based upon the Company’s ongoing review of amounts outstanding, length of collection periods, changes in reinsurer credit standing, disputes, applicable coverage defenses and other relevant factors. For structured settlements, the allowance is also based upon the Company’s ongoing review of life insurers’ creditworthiness and estimated amounts of coverage that would be available from state guaranty funds if a life insurer defaults. A probability-of-default methodology which reflects current and forecasted economic conditions is used to estimate the amount of uncollectible reinsurance due to credit-related factors and the estimate is reported in an allowance for estimated uncollectible reinsurance. The allowance also includes estimated uncollectible amounts related to dispute risk with reinsurers. Amounts deemed to be uncollectible, including amounts due from known insolvent reinsurers, are written off against the allowance. Changes in the allowance, as well as any subsequent collections of amounts previously written off, are reported as part of claims and claim adjustment expenses. The Company evaluates and monitors the financial condition of its reinsurers under voluntary reinsurance arrangements to minimize its exposure to significant losses from reinsurer insolvencies.

Contractholder Receivables and Payables [Policy Text Block]

Contractholder Receivables and Payables

Under certain workers’ compensation insurance contracts with deductible features, the Company is obligated to pay the claimant for the full amount of the claim. The Company is subsequently reimbursed by the policyholder for the deductible amount. These amounts are included on a gross basis in the consolidated balance sheet in both contractholder payables and contractholder receivables. Contractholder receivables are reported net of an allowance for expected credit losses. The allowance is based upon the Company’s ongoing review of amounts outstanding, changes in policyholder credit standing, and other relevant factors. A probability-of-default methodology which reflects current and forecasted economic conditions is used to estimate the allowance for expected credit losses.

Premiums and Unearned Premium Reserves [Policy Text Block]

Premiums and Unearned Premium Reserves

Premiums are recognized as revenues pro rata over the policy period. Unearned premium reserves represent the unexpired portion of policy premiums. Accrued retrospective premiums are included in premium balances receivable. Premium balances receivable are reported net of an allowance for expected credit losses. The allowance is based upon the Company’s ongoing review of amounts outstanding, historical loss data, including delinquencies and write-offs, current and forecasted economic conditions and other relevant factors. Credit risk is partially mitigated by the Company’s ability to cancel the policy if the policyholder does not pay the premium.