Name:	trv_EquitySecuritiesFvNi
Namespace Prefix:	trv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

No definition available.

Name:	trv_EquitySecuritiesFvNiCost
Namespace Prefix:	trv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

No definition available.

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

Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

No definition available.

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

Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

No definition available.

Name:	trv_EquitySecuritiesFvNiUnrealizedLoss
Namespace Prefix:	trv_
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.

No definition available.