Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Consolidating Statement of Cash Flows
Net income	$ 812	$ 683	$ 1,645	$ 1,735
Net adjustments to reconcile net income to net cash provided by (used in) operating activities			(770)	(407)
Net cash provided by operating activities			875	1,328
Proceeds from maturities of fixed maturities			5,314	4,915
Proceeds from sales of investments, fixed maturities			1,226	785
Proceeds from sales of investments, equity securities			28	95
Proceeds from sales of investments, real estate investments			10	5
Proceeds from sales of investments, other investments			354	338
Purchases of investments, fixed maturities			(6,239)	(5,449)
Purchases of investments, equity securities			(22)	(40)
Purchases of investments, real estate investments			(69)	(36)
Purchases of investments, other investments			(275)	(226)
Net (purchases) sales of short-term securities			433	60
Securities transactions in course of settlement			183	204
Acquisition, net of cash acquired				(12)
Other investing activities			(178)	(152)
Net cash provided by investing activities			765	487
Treasury stock acquired - share repurchase authorization			(1,400)	(1,525)
Treasury stock acquired - net employee share-based compensation			(72)	(55)
Dividends paid to shareholders			(369)	(365)
Issuance of common stock - employee share options			117	122
Excess tax benefits from share-based payment arrangements			31	24
Net cash used in financing activities			(1,693)	(1,799)
Effect of exchange rate changes on cash			(4)	1
Net increase (decrease) in cash			(57)	17
Cash at beginning of year			374	294
Cash at end of period	317	311	317	311
Income taxes paid (received)			597	727
Interest paid			183	183
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Cash Flows
Net income	628	526	1,260	1,309
Net adjustments to reconcile net income to net cash provided by (used in) operating activities			(410)	(154)
Net cash provided by operating activities			850	1,155
Proceeds from maturities of fixed maturities			3,604	3,005
Proceeds from sales of investments, fixed maturities			710	415
Proceeds from sales of investments, equity securities			11	57
Proceeds from sales of investments, other investments			244	196
Purchases of investments, fixed maturities			(4,352)	(3,399)
Purchases of investments, equity securities			(2)	(3)
Purchases of investments, real estate investments				(21)
Purchases of investments, other investments			(222)	(154)
Net (purchases) sales of short-term securities			327	347
Securities transactions in course of settlement			190	113
Acquisition, net of cash acquired				(9)
Other investing activities			(175)	(147)
Net cash provided by investing activities			335	400
Dividends paid to parent company			(1,222)	(1,525)
Net cash used in financing activities			(1,222)	(1,525)
Net increase (decrease) in cash			(37)	30
Cash at beginning of year			221	137
Cash at end of period	184	167	184	167
Income taxes paid (received)			534	570
Interest paid			24	24
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income	245	211	500	532
Net adjustments to reconcile net income to net cash provided by (used in) operating activities			(520)	(317)
Net cash provided by operating activities			(20)	215
Proceeds from maturities of fixed maturities			1,707	1,909
Proceeds from sales of investments, fixed maturities			516	369
Proceeds from sales of investments, equity securities			17	34
Proceeds from sales of investments, real estate investments			10	5
Proceeds from sales of investments, other investments			110	142
Purchases of investments, fixed maturities			(1,869)	(2,046)
Purchases of investments, equity securities			(19)	(32)
Purchases of investments, real estate investments			(69)	(15)
Purchases of investments, other investments			(53)	(72)
Net (purchases) sales of short-term securities			224	(47)
Securities transactions in course of settlement			(7)	91
Acquisition, net of cash acquired				(3)
Other investing activities			(3)	(5)
Net cash provided by investing activities			564	330
Dividends paid to parent company			(560)	(557)
Net cash used in financing activities			(560)	(557)
Effect of exchange rate changes on cash			(4)	1
Net increase (decrease) in cash			(20)	(11)
Cash at beginning of year			151	154
Cash at end of period	131	143	131	143
Income taxes paid (received)			197	205
Reportable Legal Entities [Member] | Travelers [Member]
Consolidating Statement of Cash Flows
Net income	812	683	1,645	1,735
Net adjustments to reconcile net income to net cash provided by (used in) operating activities			182	305
Net cash provided by operating activities			1,827	2,040
Proceeds from maturities of fixed maturities			3	1
Proceeds from sales of investments, fixed maturities				1
Proceeds from sales of investments, equity securities				4
Purchases of investments, fixed maturities			(18)	(4)
Purchases of investments, equity securities			(1)	(5)
Net (purchases) sales of short-term securities			(118)	(240)
Net cash provided by investing activities			(134)	(243)
Treasury stock acquired - share repurchase authorization			(1,400)	(1,525)
Treasury stock acquired - net employee share-based compensation			(72)	(55)
Dividends paid to shareholders			(369)	(365)
Issuance of common stock - employee share options			117	122
Excess tax benefits from share-based payment arrangements			31	24
Net cash used in financing activities			(1,693)	(1,799)
Net increase (decrease) in cash				(2)
Cash at beginning of year			2	3
Cash at end of period	2	1	2	1
Income taxes paid (received)			(134)	(48)
Interest paid			159	159
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income	$ (873)	$ (737)	(1,760)	(1,841)
Net adjustments to reconcile net income to net cash provided by (used in) operating activities			(22)	(241)
Net cash provided by operating activities			(1,782)	(2,082)
Dividends paid to parent company			1,782	2,082
Net cash used in financing activities			$ 1,782	$ 2,082