Contingencies, Commitments and Guarantees (details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Contingencies and Commitments disclosure
Unfunded commitments to private equity limited partnerships and real estate partnerships	$ 1,650	$ 1,630

The amount of unfunded commitments to private equity limited partnerships and real estate partnerships in which the Company invests.

No definition available.

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