Consolidating Financial Statements (details) - Consolidating Balance Sheet (Unaudited) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	$ 62,694	$ 60,515
Equity securities, available for sale, at fair value	453	732
Real estate investments	932	928
Short-term securities	4,895	4,865
Other investments	3,528	3,448
Total investments	72,502	70,488
Cash	344	307	$ 380	$ 374
Investment income accrued	606	630
Premiums receivable	7,144	6,722
Reinsurance recoverables	8,309	8,287
Ceded unearned premiums	551	589
Deferred acquisition costs	2,025	1,923	1,849
Deferred taxes	70	465
Contractholder receivables	4,775	4,609
Goodwill	3,951	3,580
Other intangible assets	342	268
Other assets	2,864	2,377
Total assets	103,483	100,245
Claims and claim adjustment expense reserves	49,650	47,949	48,295
Unearned premium reserves	12,915	12,329	11,971
Contractholder payables	4,775	4,609
Payables for reinsurance premiums	274	273
Debt	6,571	6,437
Other liabilities	5,567	5,427
Total liabilities	79,752	77,024
Common stock	22,886	22,614
Retained earnings	33,462	32,196
Accumulated other comprehensive income (loss)	(343)	(755)
Treasury stock, at cost	(32,274)	(30,834)
Total shareholders' equity	23,731	23,221	23,598
Total liabilities and shareholders' equity	103,483	100,245
Fixed maturities, available for sale, amortized cost	61,316	59,650
Equity securities, available for sale, cost	$ 440	$ 504
Common stock, shares authorized (in shares)	1,750.0	1,750.0
Common stock, shares issued (in shares)	271.5	279.6
Common stock, shares outstanding (in shares)	271.4	279.6
Treasury stock, at cost (in shares)	500.9	489.5
Travelers [Member]
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	$ 82	$ 49
Equity securities, available for sale, at fair value	181	155
Short-term securities	1,230	1,627
Cash		2	2	2
Investment in subsidiaries	27,946	27,137
Total assets	30,131	29,036
Debt	5,878	5,744
Total liabilities	6,402	5,826
Common stock	22,886	22,614
Retained earnings	33,460	32,185
Accumulated other comprehensive income (loss)	(343)	(755)
Treasury stock, at cost	(32,274)	(30,834)
Total shareholders' equity	23,729	23,210
Total liabilities and shareholders' equity	$ 30,131	$ 29,036
Common stock, shares authorized (in shares)	1,750.0	1,750.0
Common stock, shares issued (in shares)	271.5	279.6
Common stock, shares outstanding (in shares)	271.4	279.6
Treasury stock, at cost (in shares)	500.9	489.5
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	$ 43,240	$ 42,014
Equity securities, available for sale, at fair value	161	169
Real estate investments	54	56
Short-term securities	2,751	2,447
Other investments	2,673	2,569
Total investments	48,879	47,255
Cash	157	141	225	221
Investment income accrued	418	441
Premiums receivable	4,852	4,545
Reinsurance recoverables	5,842	5,664
Ceded unearned premiums	493	536
Deferred acquisition costs	1,835	1,741
Deferred taxes	(89)	216
Contractholder receivables	3,854	3,656
Goodwill	2,592	2,578
Other intangible assets	202	202
Other assets	2,181	1,973
Total assets	71,216	68,948
Claims and claim adjustment expense reserves	33,386	32,168
Unearned premium reserves	8,957	8,575
Contractholder payables	3,854	3,656
Payables for reinsurance premiums	165	156
Debt	693	693
Other liabilities	4,161	4,106
Total liabilities	51,216	49,354
Additional paid-in capital	11,634	11,634
Retained earnings	8,036	7,933
Accumulated other comprehensive income (loss)	330	27
Total shareholders' equity	20,000	19,594
Total liabilities and shareholders' equity	71,216	68,948
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	19,372	18,452
Equity securities, available for sale, at fair value	111	408
Real estate investments	878	872
Short-term securities	914	791
Other investments	854	878
Total investments	22,129	21,401
Cash	187	164	153	151
Investment income accrued	183	183
Premiums receivable	2,292	2,177
Reinsurance recoverables	2,467	2,623
Ceded unearned premiums	58	53
Deferred acquisition costs	190	182
Deferred taxes	173	224
Contractholder receivables	921	953
Goodwill	1,368	1,002
Other intangible assets	140	66
Other assets	(3)	370
Total assets	30,105	29,398
Claims and claim adjustment expense reserves	16,264	15,781
Unearned premium reserves	3,958	3,754
Contractholder payables	921	953
Payables for reinsurance premiums	109	117
Debt	14
Other liabilities	882	1,239
Total liabilities	22,148	21,844
Common stock	390	390
Additional paid-in capital	6,972	6,499
Retained earnings	594	797
Accumulated other comprehensive income (loss)	1	(132)
Total shareholders' equity	7,957	7,554
Total liabilities and shareholders' equity	30,105	29,398
Reportable Legal Entities [Member] | Travelers [Member]
Consolidating Balance Sheet
Fixed maturities, available for sale, at fair value	82	49
Equity securities, available for sale, at fair value	181	155
Short-term securities	1,230	1,627
Other investments	1	1
Total investments	1,494	1,832
Cash		2	$ 2	$ 2
Investment income accrued	5	6
Deferred taxes	(14)	25
Investment in subsidiaries	27,946	27,137
Other assets	700	34
Total assets	30,131	29,036
Debt	5,878	5,744
Other liabilities	524	82
Total liabilities	6,402	5,826
Common stock	22,886	22,614
Retained earnings	33,460	32,185
Accumulated other comprehensive income (loss)	(343)	(755)
Treasury stock, at cost	(32,274)	(30,834)
Total shareholders' equity	23,729	23,210
Total liabilities and shareholders' equity	30,131	29,036
Eliminations [Member]
Consolidating Balance Sheet
Goodwill	(9)
Investment in subsidiaries	(27,946)	(27,137)
Other assets	(14)
Total assets	(27,969)	(27,137)
Debt	(14)
Total liabilities	(14)
Common stock	(390)	(390)
Additional paid-in capital	(18,606)	(18,133)
Retained earnings	(8,628)	(8,719)
Accumulated other comprehensive income (loss)	(331)	105
Total shareholders' equity	(27,955)	(27,137)
Total liabilities and shareholders' equity	$ (27,969)	$ (27,137)