Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Consolidating Statement of Cash Flows
Net income	$ 928	$ 919	$ 2,573	$ 2,654
Net adjustments to reconcile net income to net cash provided by operating activities			101	514
Net cash provided by operating activities			2,674	3,168
Proceeds from maturities of fixed maturities			8,805	7,975
Proceeds from sales of investments, fixed maturities			1,555	927
Proceeds from sales of investments, equity securities			38	128
Proceeds from sales of investments, real estate investments			15	5
Proceeds from sales of investments, other investments			505	612
Purchases of investments, fixed maturities			(9,972)	(8,237)
Purchases of investments, equity securities			(31)	(47)
Purchases of investments, real estate investments			(116)	(41)
Purchases of investments, other investments			(389)	(406)
Net purchases of short-term securities			(782)	(1,163)
Securities transactions in course of settlement			103	119
Acquisition, net of cash acquired				(12)
Other investing activities			(222)	(262)
Net cash used in investing activities			(491)	(402)
Issuance of debt			392
Treasury stock acquired - share repurchase authorization			(2,150)	(2,275)
Treasury stock acquired - net employee share-based compensation			(73)	(56)
Dividends paid to shareholders			(557)	(549)
Issuance of common stock - employee share options			142	154
Excess tax benefits from share-based payment arrangements			42	38
Net cash used in financing activities			(2,204)	(2,688)
Effect of exchange rate changes on cash			(9)	(5)
Net increase (decrease) in cash			(30)	73
Cash at beginning of year			374	294
Cash at end of period	344	367	344	367
Income taxes paid (received)			882	785
Interest paid			217	217
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Cash Flows
Net income	699	687	1,959	1,996
Net adjustments to reconcile net income to net cash provided by operating activities			90	391
Net cash provided by operating activities			2,049	2,387
Proceeds from maturities of fixed maturities			5,929	4,886
Proceeds from sales of investments, fixed maturities			935	511
Proceeds from sales of investments, equity securities			14	83
Proceeds from sales of investments, real estate investments				1
Proceeds from sales of investments, other investments			341	317
Purchases of investments, fixed maturities			(6,845)	(4,888)
Purchases of investments, equity securities			(3)	(3)
Purchases of investments, real estate investments				(22)
Purchases of investments, other investments			(311)	(292)
Net purchases of short-term securities			(172)	(552)
Securities transactions in course of settlement			80	66
Acquisition, net of cash acquired				(9)
Other investing activities			(262)	(256)
Net cash used in investing activities			(294)	(158)
Dividends paid to parent company			(1,774)	(2,150)
Net cash used in financing activities			(1,774)	(2,150)
Effect of exchange rate changes on cash			(1)
Net increase (decrease) in cash			(20)	79
Cash at beginning of year			221	137
Cash at end of period	201	216	201	216
Income taxes paid (received)			748	684
Interest paid			40	40
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income	287	285	787	817
Net adjustments to reconcile net income to net cash provided by operating activities			(247)	(73)
Net cash provided by operating activities			540	744
Proceeds from maturities of fixed maturities			2,869	3,088
Proceeds from sales of investments, fixed maturities			620	415
Proceeds from sales of investments, equity securities			24	41
Proceeds from sales of investments, real estate investments			15	4
Proceeds from sales of investments, other investments			164	295
Purchases of investments, fixed maturities			(3,103)	(3,345)
Purchases of investments, equity securities			(26)	(38)
Purchases of investments, real estate investments			(116)	(19)
Purchases of investments, other investments			(78)	(114)
Net purchases of short-term securities			(184)	(326)
Securities transactions in course of settlement			23	53
Acquisition, net of cash acquired				(3)
Other investing activities			40	(6)
Net cash used in investing activities			248	45
Dividends paid to parent company			(790)	(789)
Net cash used in financing activities			(790)	(789)
Effect of exchange rate changes on cash			(8)	(5)
Net increase (decrease) in cash			(10)	(5)
Cash at beginning of year			151	154
Cash at end of period	141	149	141	149
Income taxes paid (received)			286	215
Reportable Legal Entities [Member] | Travelers [Member]
Consolidating Statement of Cash Flows
Net income	928	919	2,573	2,654
Net adjustments to reconcile net income to net cash provided by operating activities			76	322
Net cash provided by operating activities			2,649	2,976
Proceeds from maturities of fixed maturities			7	1
Proceeds from sales of investments, fixed maturities				1
Proceeds from sales of investments, equity securities				4
Purchases of investments, fixed maturities			(24)	(4)
Purchases of investments, equity securities			(2)	(6)
Net purchases of short-term securities			(426)	(285)
Net cash used in investing activities			(445)	(289)
Issuance of debt			392
Treasury stock acquired - share repurchase authorization			(2,150)	(2,275)
Treasury stock acquired - net employee share-based compensation			(73)	(56)
Dividends paid to shareholders			(557)	(549)
Issuance of common stock - employee share options			142	154
Excess tax benefits from share-based payment arrangements			42	38
Net cash used in financing activities			(2,204)	(2,688)
Net increase (decrease) in cash				(1)
Cash at beginning of year			2	3
Cash at end of period	2	2	2	2
Income taxes paid (received)			(152)	(114)
Interest paid			177	177
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income	$ (986)	$ (972)	(2,746)	(2,813)
Net adjustments to reconcile net income to net cash provided by operating activities			182	(126)
Net cash provided by operating activities			(2,564)	(2,939)
Dividends paid to parent company			2,564	2,939
Net cash used in financing activities			$ 2,564	$ 2,939