Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
Segment Information (Details) $ in Millions	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) segment	Jun. 30, 2024 USD ($)
Segment reporting information
Number of reportable business segments \| segment			3
Premiums	$ 10,921	$ 10,243	$ 21,631	$ 20,369
Net investment income	942	885	1,872	1,731
Fee income	124	115	243	224
Other revenues	123	105	235	217
Claims and claim adjustment expenses	6,789	7,373	14,795	14,029
Amortization of deferred acquisition costs	1,802	1,678	3,580	3,376
General and administrative expenses	1,545	1,478	3,004	2,884
Income tax expense (benefit)	372	122	445	369
Net realized investment gains (losses)	6	(65)	(55)	(30)
Total revenues	12,116	11,283	23,926	22,511
Core income (loss)	1,504	585	1,947	1,681
Net realized investment gains (losses), net of tax	5	(51)	(43)	(24)
Net income	1,509	534	1,904	1,657
Reportable Segments [Member]
Segment reporting information
Premiums	10,921	10,243	21,631	20,369
Net investment income	942	885	1,872	1,731
Fee income	124	115	243	224
Other revenues	123	105	235	217
Total segment revenues	12,110	11,348	23,981	22,541
Claims and claim adjustment expenses	6,789	7,373	14,795	14,029
Amortization of deferred acquisition costs	1,802	1,678	3,580	3,376
General and administrative expenses	1,533	1,466	2,981	2,864
Income tax expense (benefit)	395	158	505	420
Core income (loss)	1,591	673	2,120	1,852
Reportable Segments [Member] \| Business Insurance [Member]
Segment reporting information
Premiums	5,545	5,168	11,010	10,328
Net investment income	662	632	1,318	1,241
Fee income	111	105	219	206
Other revenues	95	77	177	154
Total segment revenues	6,413	5,982	12,724	11,929
Claims and claim adjustment expenses	3,584	3,471	7,289	6,802
Amortization of deferred acquisition costs	944	861	1,861	1,725
General and administrative expenses	875	835	1,722	1,653
Income tax expense (benefit)	197	159	356	329
Core income (loss)	813	656	1,496	1,420
Reportable Segments [Member] \| Business Insurance [Member] \| Domestic [Member]
Segment reporting information
Premiums	5,083	4,736	10,065	9,483
Reportable Segments [Member] \| Business Insurance [Member] \| Domestic [Member] \| Workers' compensation [Member]
Segment reporting information
Premiums	841	864	1,664	1,744
Reportable Segments [Member] \| Business Insurance [Member] \| Domestic [Member] \| Automobile [Member]
Segment reporting information
Premiums	968	874	1,910	1,734
Reportable Segments [Member] \| Business Insurance [Member] \| Domestic [Member] \| Commercial property [Member]
Segment reporting information
Premiums	960	894	1,897	1,767
Reportable Segments [Member] \| Business Insurance [Member] \| Domestic [Member] \| General liability [Member]
Segment reporting information
Premiums	862	845	1,723	1,692
Reportable Segments [Member] \| Business Insurance [Member] \| Domestic [Member] \| Commercial multi-peril [Member]
Segment reporting information
Premiums	1,435	1,246	2,835	2,516
Reportable Segments [Member] \| Business Insurance [Member] \| Domestic [Member] \| Other [Member]
Segment reporting information
Premiums	17	13	36	30
Reportable Segments [Member] \| Business Insurance [Member] \| International [Member]
Segment reporting information
Premiums	462	432	945	845
Reportable Segments [Member] \| Bond & Specialty Insurance [Member]
Segment reporting information
Premiums	1,021	977	2,016	1,933
Net investment income	107	94	209	184
Fee income	0	0	0	0
Other revenues	5	6	11	15
Total segment revenues	1,133	1,077	2,236	2,132
Claims and claim adjustment expenses	418	473	852	901
Amortization of deferred acquisition costs	195	183	382	365
General and administrative expenses	214	207	419	412
Income tax expense (benefit)	62	44	119	89
Core income (loss)	244	170	464	365
Reportable Segments [Member] \| Bond & Specialty Insurance [Member] \| Domestic [Member]
Segment reporting information
Premiums	885	845	1,753	1,667
Reportable Segments [Member] \| Bond & Specialty Insurance [Member] \| Domestic [Member] \| General liability [Member]
Segment reporting information
Premiums	459	437	911	863
Reportable Segments [Member] \| Bond & Specialty Insurance [Member] \| Domestic [Member] \| Fidelity and surety [Member]
Segment reporting information
Premiums	367	350	725	690
Reportable Segments [Member] \| Bond & Specialty Insurance [Member] \| Domestic [Member] \| Other [Member]
Segment reporting information
Premiums	59	58	117	114
Reportable Segments [Member] \| Bond & Specialty Insurance [Member] \| International [Member]
Segment reporting information
Premiums	136	132	263	266
Reportable Segments [Member] \| Personal Insurance [Member]
Segment reporting information
Premiums	4,355	4,098	8,605	8,108
Net investment income	173	159	345	306
Fee income	13	10	24	18
Other revenues	23	22	47	48
Total segment revenues	4,564	4,289	9,021	8,480
Claims and claim adjustment expenses	2,787	3,429	6,654	6,326
Amortization of deferred acquisition costs	663	634	1,337	1,286
General and administrative expenses	444	424	840	799
Income tax expense (benefit)	136	(45)	30	2
Core income (loss)	534	(153)	160	67
Reportable Segments [Member] \| Personal Insurance [Member] \| Domestic [Member]
Segment reporting information
Premiums	4,183	3,933	8,268	7,779
Reportable Segments [Member] \| Personal Insurance [Member] \| Domestic [Member] \| Automobile [Member]
Segment reporting information
Premiums	1,980	1,919	3,944	3,793
Reportable Segments [Member] \| Personal Insurance [Member] \| Domestic [Member] \| Homeowners and Other [Member]
Segment reporting information
Premiums	2,203	2,014	4,324	3,986
Reportable Segments [Member] \| Personal Insurance [Member] \| International [Member]
Segment reporting information
Premiums	172	165	337	329
Other [Member]
Segment reporting information
Core income (loss)	(87)	(88)	(173)	(171)
After-tax interest expense	$ 78	$ 78	$ 156	$ 155

TRAVELERS COMPANIES, INC. 10-Q