Share-based Incentive Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Feb. 06, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Summary of stock option activity [Roll Forward]
Stock options outstanding, beginning of year, number (in shares)		8,558,864
Stock options granted, number (in shares)		875,760
Stock options exercised, number (in shares)		(944,913)
Stock options forfeited or expired, number (in shares)		(66,729)
Stock options outstanding, end of year, number (in shares)		8,422,982	8,558,864
Stock options outstanding, beginning of year, weighted average exercise price (in dollars per share)		$ 134.92
Stock options granted, weighted average exercise price (in dollars per share)		189.00
Stock options exercised, weighted average exercise price (in dollars per share)		121.73
Stock options forfeited or expired, weighted average exercise price (in dollars per share)		160.27
Stock options outstanding, end of year, weighted average exercise price (in dollars per share)		$ 141.82	$ 134.92
Stock options outstanding, weighted average contractual life remaining (in years)		5 years 9 months 18 days
Stock options outstanding, aggregate intrinsic value		$ 410
Stock options vested at end of year, number (in shares)		7,312,505
Stock options vested at end of year, weighted average exercise price (in dollars per share)		$ 138.44
Stock options vested at end of year, weighted average contractual life remaining (in years)		5 years 6 months
Stock options vested at end of year, aggregate intrinsic value		$ 381
Stock options exercisable at end of year, number (in shares)		5,181,130
Stock options exercisable at end of year, weighted average exercise price (in dollars per share)		$ 128.55
Stock options exercisable at end of year, weighted average contractual life remaining (in years)		4 years 6 months
Stock options exercisable at end of year, aggregate intrinsic value		$ 321
Stock option grants [Member]
Share-based compensation plan description
Option term		10 years
Award vesting period		3 years
Assumptions used in estimating fair value of options
Expected term of stock options		6 years	6 years	6 years
Expected volatility of Company’s stock (percent)			24.81%
Weighted average volatility (percent)		25.63%	24.81%	24.22%
Expected annual dividend per share (in dollars per share)		$ 3.72	$ 3.52
Risk-free rate			1.83%
Stock options granted, weighted average grant-date fair value of options granted (in dollars per share)		$ 47.77	$ 35.70	$ 23.32
Total intrinsic value of options exercised during the year		$ 58	$ 110	$ 94
Stock option grants [Member] | Minimum [Member]
Assumptions used in estimating fair value of options
Expected volatility of Company’s stock (percent)		25.63%		24.22%
Expected annual dividend per share (in dollars per share)				$ 3.40
Risk-free rate		3.63%		0.59%
Stock option grants [Member] | Maximum [Member]
Assumptions used in estimating fair value of options
Expected volatility of Company’s stock (percent)		25.99%		24.53%
Expected annual dividend per share (in dollars per share)				$ 3.52
Risk-free rate		3.89%		1.08%
Director deferred stock awards [Member]
Share-based compensation plan description
Number of days prior to date of annual meeting in year following date of grant in which annual deferred stock awards vest in full		1 day
Number of months after termination of service as a director before distributions of deferred stock awards begin		6 months
The Travelers Companies, Inc 2023 Stock Incentive Plan [Member]
Share-based compensation plan description
Number of shares of the Company's common stock authorized for grant under the 2023 Incentive Plan, total (in shares)		5,789,184
The Travelers Companies, Inc 2023 Stock Incentive Plan [Member] | Stock option grants [Member] | Subsequent event [Member]
Assumptions used in estimating fair value of options
Stock options granted, weighted average grant-date fair value of options granted (in dollars per share)	$ 56.45
Summary of stock option activity [Roll Forward]
Stock options granted, number (in shares)	770,664
Stock options granted, weighted average exercise price (in dollars per share)	$ 213.01