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Namespace Prefix:	trv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The percentage of employer contributions and related earnings in which the employee is vested.

No definition available.

Name:	trv_EBPEmployerContributionAndRelatedEarningsVestingPercentage
Namespace Prefix:	trv_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Period after which an employee becomes fully vested in their employer matching contributions and related earnings.

No definition available.

Name:	trv_EBPEmployerContributionAndRelatedEarningsVestingServicePeriod
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Age at which a participant will become vested in full while employed, if not already vested

No definition available.

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Data Type:	xbrli:integerItemType
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Period Type:	duration

Maximum contribution amount that the employer may match per employee.

No definition available.

Name:	trv_EBPEmployerContributionParticipantCompensationMatchAmount
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan.

No definition available.

Name:	trv_EBPForfeitedNonvestedAccountDecreaseTotal
Namespace Prefix:	trv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of prior months used to determine highest outstanding loan balance when calculating amount of maximum account balance that participant in employee stock purchase, saving, or similar plan can borrow.

No definition available.

Name:	trv_EBPNoteReceivableFromParticipantAccountMaximumBorrowingAmountMonthsPriorUsedToDetermineHighestLoanOutstandingBalance
Namespace Prefix:	trv_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Maximum number of loans each participant can have outstanding at any one time.

No definition available.

Name:	trv_EBPNoteReceivableFromParticipantMaximumNumberOfLoansPerParticipant
Namespace Prefix:	trv_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Maximum repayment period for non-primary residence participant loan in employee stock purchase, saving, or similar plan

No definition available.

Name:	trv_EBPNoteReceivableFromParticipantNonPrimaryResidenceLoanMaximumBorrowingTerm
Namespace Prefix:	trv_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Number of participant loans outstanding in employee stock purchase, saving, or similar plan.

No definition available.

Name:	trv_EBPNoteReceivableFromParticipantNumberOfLoansOutstanding
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Amount of one-time set-up fee charged per participant loan in employee stock purchase, saving, or similar plan.

No definition available.

Name:	trv_EBPNoteReceivableFromParticipantOneTimeSetUpFeePerLoan
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Maximum repayment period for primary residence participant loan in employee stock purchase, saving, or similar plan

No definition available.

Name:	trv_EBPNoteReceivableFromParticipantPrimaryResidenceLoanMaximumBorrowingTerm
Namespace Prefix:	trv_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Amount of quarterly loan maintenance fee charged per participant loan in employee stock purchase, saving, or similar plan.

No definition available.

Name:	trv_EBPNoteReceivableFromParticipantQuarterlyMaintenanceFeePerLoan
Namespace Prefix:	trv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The percentage of participant contributions, supplemental contributions, and related earnings in which the employee is vested.

No definition available.

Name:	trv_EBPParticipantContributionAndRelatedEarningsVestingPercentage
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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of maximum pretax annual eligible compensation that participant in employee stock purchase, saving, or similar plan, is permitted to contribute to total pretax annual eligible compensation.

No definition available.

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage added to reference rate used to compute variable rate on investment.

No definition available.

Name:	trv_EBPParticipantLoanBasisSpreadOnVariableRate
Namespace Prefix:	trv_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Maximum account balance amount to trigger automatic rollover to IRA upon participant termination of employment when no distribution instructions were provided.

No definition available.

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Namespace Prefix:	trv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Minimum account balance amount to trigger automatic rollover to IRA upon participant termination of employment when no distribution instructions were provided.

No definition available.

Name:	trv_EBPParticipantVestedBalanceRolledOverToIRAWhenNoDistributionInstructionsHaveBeenProvidedFollowingEmploymentTerminationMinimum
Namespace Prefix:	trv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Maximum number of days after distribution for a contribution to be considered a rollover contribution

No definition available.

Name:	trv_EBPRolloverContributionMaximumDaysAfterDistribution
Namespace Prefix:	trv_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of increase in net asset available for benefit from cash contribution from employer of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Percentage of employer matching contribution on eligible participant contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanEmployerContributionMatchingPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of participant compensation eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Amount of plan asset, in forfeited nonvested account, no longer allocated to participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount
Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of unpaid principal plus accrued but unpaid interest for loan from participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule II))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478642/962-310-45-2

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow to total participant account balance.

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Amount of minimum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Percentage of eligible compensation contributed for participant automatically enrolled in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

Name:	us-gaap-ebp_EmployeeBenefitPlanParticipantContributionAutomaticDeferralRate
Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Name:	dei_LegalEntityAxis=trv_EBP002Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	trv_EBPEmployerContributionTypeAxis=trv_EBPEmployerMatchingContributionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	trv_EBPEmployerContributionTypeAxis=trv_EBPSupplementalContributionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: