Pension Plans, Retirement Benefits and Savings Plan (details) - Savings Plan (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Savings Plan
Maximum annual match	$ 6,000
Vesting percentage of employer match after vesting period	100.00%
Vesting period	3 years
Expense related to all savings plans	$ 103,000,000	$ 100,000,000	$ 92,000,000
Maxiumum [Member]
Savings Plan
Matching contribution as a percent of eligible pay	5.00%

Period over which an employee vests in the employer matching contribution.

No definition available.

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Namespace Prefix:	trv_
Data Type:	xbrli:durationItemType
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Period Type:	duration

- Definition

Maximum amount the employer may match per employee contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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

- Definition

The percentage which the employee vests in employer matching contributions after the vesting period expires.

+ References

No definition available.

+ Details

Name:	trv_DefinedContributionPlanVestingPercentageAfterVestingPeriod
Namespace Prefix:	trv_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DefinedContributionPlanDisclosureLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: