Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidating Statement of Cash Flows
Net income	$ 3,692	$ 3,673	$ 2,473
Net adjustments to reconcile net income to net cash provided by operating activities	1	143	757
Net cash provided by operating activities	3,693	3,816	3,230
Proceeds from maturities of fixed maturities	10,894	7,904	8,369
Proceeds from sales of investments, fixed maturities	1,049	1,635	1,087
Proceeds from sales of investments, equity securities	158	86	37
Proceeds from sales of investments, real estate investments	15	18	53
Proceeds from sales of investments, other investments	855	762	835
Purchases of investments, fixed maturities	(11,325)	(9,467)	(10,447)
Purchases of investments, equity securities	(52)	(57)	(48)
Purchases of investments, real estate investments	(48)	(107)	(95)
Purchases of investments, other investments	(554)	(446)	(534)
Net sales (purchases) of short-term securities	(498)	111	117
Securities transactions in course of settlement	82	21	(23)
Acquisition, net of cash acquired	(12)	(997)
Other investing activities	(358)	(373)	(323)
Net cash provided by (used in) investing activities	206	(910)	(972)
Treasury stock acquired - share repurchase authorization	(3,275)	(2,400)	(1,474)
Treasury stock acquired - net employee share-based compensation	(57)	(61)	(53)
Dividends paid to shareholders	(729)	(729)	(694)
Issuance of common stock - employee share options	195	206	295
Payment of debt		(500)	(258)
Issuance of debt		494
Excess tax benefits from share-based payment arrangements	57	51	38
Net cash used in financing activities	(3,809)	(2,939)	(2,146)
Effect of exchange rate changes on cash	(10)	(3)	4
Net increase (decrease) in cash	80	(36)	116
Cash at beginning of year	294	330	214
Cash at end of year	374	294	330
Income taxes paid (received)	1,147	1,057	188
Interest paid	365	355	375
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Cash Flows
Net income	2,780	2,771	1,857
Net adjustments to reconcile net income to net cash provided by operating activities	343	(497)	715
Net cash provided by operating activities	3,123	2,274	2,572
Proceeds from maturities of fixed maturities	6,625	5,484	5,905
Proceeds from sales of investments, fixed maturities	595	989	730
Proceeds from sales of investments, equity securities	111	45	21
Proceeds from sales of investments, real estate investments	1
Proceeds from sales of investments, other investments	477	489	555
Purchases of investments, fixed maturities	(6,856)	(6,260)	(7,361)
Purchases of investments, equity securities	(3)	(21)	(18)
Purchases of investments, real estate investments	(22)	(1)
Purchases of investments, other investments	(405)	(320)	(371)
Net sales (purchases) of short-term securities	(268)	(272)	(308)
Securities transactions in course of settlement	44	(2)	14
Acquisition, net of cash acquired	(9)	(773)
Other investing activities	(350)	(365)	(323)
Net cash provided by (used in) investing activities	(60)	(1,007)	(1,156)
Payment of debt		(500)
Dividends paid to parent company	(2,978)	(1,307)	(1,353)
Capital contributions, loans and other transactions between subsidiaries		500
Net cash used in financing activities	(2,978)	(1,307)	(1,353)
Effect of exchange rate changes on cash	(1)
Net increase (decrease) in cash	84	(40)	63
Cash at beginning of year	137	177	114
Cash at end of year	221	137	177
Income taxes paid (received)	947	942	287
Interest paid	47	60	73
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income	1,124	1,044	798
Net adjustments to reconcile net income to net cash provided by operating activities	(293)	413	7
Net cash provided by operating activities	831	1,457	805
Proceeds from maturities of fixed maturities	4,258	2,419	2,462
Proceeds from sales of investments, fixed maturities	453	641	355
Proceeds from sales of investments, equity securities	43	41	16
Proceeds from sales of investments, real estate investments	14	18	53
Proceeds from sales of investments, other investments	378	273	280
Purchases of investments, fixed maturities	(4,465)	(3,201)	(3,077)
Purchases of investments, equity securities	(42)	(34)	(28)
Purchases of investments, real estate investments	(26)	(106)	(95)
Purchases of investments, other investments	(149)	(126)	(163)
Net sales (purchases) of short-term securities	(223)	(52)	44
Securities transactions in course of settlement	38	24	(36)
Acquisition, net of cash acquired	(3)	(224)
Other investing activities	(8)	(8)
Net cash provided by (used in) investing activities	268	(335)	(189)
Dividends paid to parent company	(1,093)	(1,116)	(567)
Net cash used in financing activities	(1,093)	(1,116)	(567)
Effect of exchange rate changes on cash	(9)	(3)	4
Net increase (decrease) in cash	(3)	3	53
Cash at beginning of year	154	151	98
Cash at end of year	151	154	151
Income taxes paid (received)	336	325	108
Reportable Legal Entities [Member] | Travelers [Member]
Consolidating Statement of Cash Flows
Net income	3,692	3,673	2,473
Net adjustments to reconcile net income to net cash provided by operating activities	118	(1,665)	(700)
Net cash provided by operating activities	3,810	2,008	1,773
Proceeds from maturities of fixed maturities	11	1	2
Proceeds from sales of investments, fixed maturities	1	5	2
Proceeds from sales of investments, equity securities	4
Purchases of investments, fixed maturities	(4)	(6)	(9)
Purchases of investments, equity securities	(7)	(2)	(2)
Net sales (purchases) of short-term securities	(7)	435	381
Securities transactions in course of settlement		(1)	(1)
Net cash provided by (used in) investing activities	(2)	432	373
Treasury stock acquired - share repurchase authorization	(3,275)	(2,400)	(1,474)
Treasury stock acquired - net employee share-based compensation	(57)	(61)	(53)
Dividends paid to shareholders	(729)	(729)	(694)
Issuance of common stock - employee share options	195	206	295
Payment of debt			(258)
Issuance of debt		494
Excess tax benefits from share-based payment arrangements	57	51	38
Net cash used in financing activities	(3,809)	(2,439)	(2,146)
Net increase (decrease) in cash	(1)	1
Cash at beginning of year	3	2	2
Cash at end of year	2	3	2
Income taxes paid (received)	(136)	(210)	(207)
Interest paid	318	295	302
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income	(3,904)	(3,815)	(2,655)
Net adjustments to reconcile net income to net cash provided by operating activities	(167)	1,892	735
Net cash provided by operating activities	(4,071)	(1,923)	(1,920)
Dividends paid to parent company	4,071	2,423	1,920
Capital contributions, loans and other transactions between subsidiaries		(500)
Net cash used in financing activities	$ 4,071	$ 1,923	$ 1,920