Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Consolidating Statement of Cash Flows
Net income	$ 866	$ 928	$ 812	$ 833	$ 1,038	$ 919	$ 683	$ 1,052	$ 3,439	$ 3,692	$ 3,673
Net adjustments to reconcile net income to net cash provided by operating activities									(5)	1	143
Net cash provided by operating activities									3,434	3,693	3,816
Proceeds from maturities of fixed maturities									11,116	10,894	7,904
Proceeds from sales of investments, fixed maturities									1,950	1,049	1,635
Proceeds from sales of investments, equity securities									59	158	86
Proceeds from sales of investments, real estate investments									31	15	18
Proceeds from sales of investments, other investments									713	855	762
Purchases of investments, fixed maturities									(12,090)	(11,325)	(9,467)
Purchases of investments, equity securities									(49)	(52)	(57)
Purchases of investments, real estate investments									(123)	(48)	(107)
Purchases of investments, other investments									(534)	(554)	(446)
Net sales (purchases) of short-term securities									(326)	(498)	111
Securities transactions in course of settlement									(113)	82	21
Acquisition, net of cash acquired									(13)	(12)	(997)
Other investing activities									(304)	(358)	(373)
Net cash provided by (used in) investing activities									317	206	(910)
Treasury stock acquired - share repurchase authorization									(3,150)	(3,275)	(2,400)
Treasury stock acquired - net employee share-based compensation									(74)	(57)	(61)
Dividends paid to shareholders									(739)	(729)	(729)
Payment of debt									(400)		(500)
Issuance of debt									392		494
Issuance of common stock - employee share options									183	195	206
Excess tax benefits from share-based payment arrangements									55	57	51
Net cash used in financing activities									(3,733)	(3,809)	(2,939)
Effect of exchange rate changes on cash									(12)	(10)	(3)
Net increase (decrease) in cash									6	80	(36)
Cash at beginning of year				374				294	374	294	330
Cash at end of year	380				374				380	374	294
Income taxes paid (received)									1,207	1,147	1,057
Interest paid									365	365	355
TPC [Member]
Consolidating Statement of Cash Flows
Net income									2,666	2,780	2,771
Net adjustments to reconcile net income to net cash provided by operating activities									(577)	343	(497)
Net cash provided by operating activities									2,089	3,123	2,274
Proceeds from maturities of fixed maturities									7,543	6,625	5,484
Proceeds from sales of investments, fixed maturities									1,227	595	989
Proceeds from sales of investments, equity securities									25	111	45
Proceeds from sales of investments, real estate investments										1
Proceeds from sales of investments, other investments									503	477	489
Purchases of investments, fixed maturities									(8,276)	(6,856)	(6,260)
Purchases of investments, equity securities									(3)	(3)	(21)
Purchases of investments, real estate investments									(1)	(22)	(1)
Purchases of investments, other investments									(423)	(405)	(320)
Net sales (purchases) of short-term securities									179	(268)	(272)
Securities transactions in course of settlement									(52)	44	(2)
Acquisition, net of cash acquired									(13)	(9)	(773)
Other investing activities									(343)	(350)	(365)
Net cash provided by (used in) investing activities									366	(60)	(1,007)
Payment of debt											(500)
Dividends paid to parent company									(2,450)	(2,978)	(1,307)
Capital contributions, loans and other transactions between subsidiaries											500
Net cash used in financing activities									(2,450)	(2,978)	(1,307)
Effect of exchange rate changes on cash									(1)	(1)
Net increase (decrease) in cash									4	84	(40)
Cash at beginning of year				221				137	221	137	177
Cash at end of year	225				221				225	221	137
Income taxes paid (received)									1,032	947	942
Interest paid									47	47	60
Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income									998	1,124	1,044
Net adjustments to reconcile net income to net cash provided by operating activities									414	(293)	413
Net cash provided by operating activities									1,412	831	1,457
Proceeds from maturities of fixed maturities									3,563	4,258	2,419
Proceeds from sales of investments, fixed maturities									723	453	641
Proceeds from sales of investments, equity securities									34	43	41
Proceeds from sales of investments, real estate investments									31	14	18
Proceeds from sales of investments, other investments									210	378	273
Purchases of investments, fixed maturities									(3,787)	(4,465)	(3,201)
Purchases of investments, equity securities									(43)	(42)	(34)
Purchases of investments, real estate investments									(122)	(26)	(106)
Purchases of investments, other investments									(111)	(149)	(126)
Net sales (purchases) of short-term securities									(489)	(223)	(52)
Securities transactions in course of settlement									(61)	38	24
Acquisition, net of cash acquired										(3)	(224)
Other investing activities									39	(8)	(8)
Net cash provided by (used in) investing activities									(13)	268	(335)
Dividends paid to parent company									(1,383)	(1,093)	(1,116)
Capital contributions, loans and other transactions between subsidiaries									(3)
Net cash used in financing activities									(1,386)	(1,093)	(1,116)
Effect of exchange rate changes on cash									(11)	(9)	(3)
Net increase (decrease) in cash									2	(3)	3
Cash at beginning of year				151				154	151	154	151
Cash at end of year	153				151				153	151	154
Income taxes paid (received)									384	336	325
Travelers [Member]
Consolidating Statement of Cash Flows
Net income									3,439	3,692	3,673
Net adjustments to reconcile net income to net cash provided by operating activities									330	118	(1,665)
Net cash provided by operating activities									3,769	3,810	2,008
Proceeds from maturities of fixed maturities									10	11	1
Proceeds from sales of investments, fixed maturities										1	5
Proceeds from sales of investments, equity securities										4
Purchases of investments, fixed maturities									(27)	(4)	(6)
Purchases of investments, equity securities									(3)	(7)	(2)
Net sales (purchases) of short-term securities									(16)	(7)	435
Securities transactions in course of settlement											(1)
Net cash provided by (used in) investing activities									(36)	(2)	432
Treasury stock acquired - share repurchase authorization									(3,150)	(3,275)	(2,400)
Treasury stock acquired - net employee share-based compensation									(74)	(57)	(61)
Dividends paid to shareholders									(739)	(729)	(729)
Payment of debt									(400)
Issuance of debt									392		494
Issuance of common stock - employee share options									183	195	206
Excess tax benefits from share-based payment arrangements									55	57	51
Net cash used in financing activities									(3,733)	(3,809)	(2,439)
Net increase (decrease) in cash										(1)	1
Cash at beginning of year				$ 2				$ 3	2	3	2
Cash at end of year	$ 2				$ 2				2	2	3
Income taxes paid (received)									(209)	(136)	(210)
Interest paid									318	318	295
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income									(3,664)	(3,904)	(3,815)
Net adjustments to reconcile net income to net cash provided by operating activities									(172)	(167)	1,892
Net cash provided by operating activities									(3,836)	(4,071)	(1,923)
Dividends paid to parent company									3,833	4,071	2,423
Capital contributions, loans and other transactions between subsidiaries									3		(500)
Net cash used in financing activities									$ 3,836	$ 4,071	$ 1,923