Share-Based Incentive Compensation (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Feb. 04, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Restricted stock units, deferred stock units and performance share awards [Member]
Share-based compensation
Fair value of shares that vested during the year		$ 253	$ 164	$ 159
Restricted stock units, deferred stock units and performance share awards [Member] | The Travelers Companies, Inc 2023 Stock Incentive Plan [Member] | Subsequent event [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, granted, number (in shares)	685,943
Restricted and deferred stock units [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, nonvested, number, beginning of year (in shares)		1,025,695
Other equity instruments, granted, number (in shares)		632,770
Other equity instruments, vested, number (in shares)		(500,718)
Other equity instruments, forfeited, number (in shares)		(56,758)
Other equity instruments, nonvested, number, end of year (in shares)		1,100,989	1,025,695
Other equity instruments, nonvested, weighted average grant-date fair value, beginning of year (in dollars per share)		$ 167.98
Other equity instruments, granted, weighted average grant-date fair value (in dollars per share)		210.23
Other equity instruments, vested, weighted average grant-date fair value (in dollars per share)		164.60
Other equity instruments, forfeited, weighted average grant-date fair value (in dollars per share)		186.74
Other equity instruments, nonvested, weighted average grant-date fair value, end of year (in dollars per share)		$ 192.83	$ 167.98
Other equity instruments, nonvested dividend equivalents, number, beginning of year (in shares)		260
Other equity instruments, nonvested dividend equivalents, number, end of year (in shares)		165	260
Restricted and deferred stock units [Member] | The Travelers Companies, Inc 2023 Stock Incentive Plan [Member] | Subsequent event [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, granted, number (in shares)	432,987
Other equity instruments, granted, weighted average grant-date fair value (in dollars per share)	$ 244.06
Restricted stock units [Member]
Share-based compensation
Award vesting period		3 years
Performance shares [Member]
Share-based compensation
Performance period		3 years
Award vesting period		3 years
Percentage of performance shares to vest if minimum performance threshold is not met		0.00%
Summary of other equity instruments [Roll Forward]
Other equity instruments, nonvested, number, beginning of year (in shares)		1,004,799
Other equity instruments, granted, number (in shares)		282,921
Other equity instruments, vested, number (in shares)		(575,266)
Other equity instruments, forfeited, number (in shares)		(9,156)
Other equity instruments, performance-based adjustment, number (in shares)		452,350
Other equity instruments, nonvested, number, end of year (in shares)		1,155,648	1,004,799
Other equity instruments, nonvested, weighted average grant-date fair value, beginning of year (in dollars per share)		$ 180.87
Other equity instruments, granted, weighted average grant-date fair value (in dollars per share)		213.01
Other equity instruments, vested, weighted average grant-date fair value (in dollars per share)		172.50
Other equity instruments, forfeited, weighted average grant-date fair value (in dollars per share)		189.68
Other equity instruments, performance-based adjustment, weighted average grant-date fair value (in dollars per share)		200.86
Other equity instruments, nonvested, weighted average grant-date fair value, end of year (in dollars per share)		$ 200.66	$ 180.87
Other equity instruments, nonvested dividend equivalents, number, beginning of year (in shares)		33,757
Other equity instruments, nonvested dividend equivalents, number, end of year (in shares)		35,112	33,757
Performance shares [Member] | Minimum [Member]
Share-based compensation
Percentage of performance shares to vest if minimum performance threshold is met or exceeded		50.00%	50.00%
Performance shares [Member] | Minimum [Member] | Subsequent event [Member]
Share-based compensation
Percentage of performance shares to vest if minimum performance threshold is met or exceeded	0.00%
Performance shares [Member] | Maximum [Member]
Share-based compensation
Percentage of performance shares to vest if minimum performance threshold is met or exceeded		200.00%	200.00%
Performance shares [Member] | Maximum [Member] | Subsequent event [Member]
Share-based compensation
Percentage of performance shares to vest if minimum performance threshold is met or exceeded	200.00%
Performance shares [Member] | The Travelers Companies, Inc 2023 Stock Incentive Plan [Member] | Subsequent event [Member]
Summary of other equity instruments [Roll Forward]
Other equity instruments, granted, number (in shares)	252,956
Other equity instruments, granted, weighted average grant-date fair value (in dollars per share)	$ 251.19