Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 1,305	$ 475
Net adjustments to reconcile net income to net cash provided by operating activities	(40)	426
Net cash provided by operating activities	1,265	901
Proceeds from maturities of fixed maturities	4,167	3,234
Proceeds from sales of investments, fixed maturities	542	736
Proceeds from sales of investments, equity securities	22	47
Proceeds from sales of investments, real estate investments	3
Proceeds from sales of investments, other investments	386	285
Purchases of investments, fixed maturities	(5,200)	(3,547)
Purchases of investments, equity securities	(33)	(103)
Purchases of investments, real estate investments	(58)	(35)
Purchases of investments, other investments	(221)	(629)
Net sales (purchases) of short-term securities	367	597
Securities transactions in course of settlement	77	213
Other investing activities	(133)	(143)
Net cash provided by (used in) investing activities	(81)	655
Payment of debt	(258)	(8)
Dividends paid to shareholders	(341)	(329)
Issuance of common stock - employee share options	170	245
Treasury shares acquired - share repurchase authorization	(707)	(1,360)
Treasury shares acquired - net employee share-based compensation	(52)	(46)
Excess tax benefits from share-based payment arrangements	19	11
Net cash used in financing activities	(1,169)	(1,487)
Effect of exchange rate changes on cash	1	4
Net increase in cash	16	73
Cash at beginning of year	214	200
Cash at end of period	230	273
Income taxes paid (received)	296	291
Interest paid	191	191
TPC [Member]
Net income	1,012	456
Net adjustments to reconcile net income to net cash provided by operating activities	109	355
Net cash provided by operating activities	1,121	811
Proceeds from maturities of fixed maturities	2,817	1,969
Proceeds from sales of investments, fixed maturities	368	382
Proceeds from sales of investments, equity securities	15	15
Proceeds from sales of investments, other investments	297	183
Purchases of investments, fixed maturities	(3,744)	(2,342)
Purchases of investments, equity securities	(2)
Purchases of investments, real estate investments		(24)
Purchases of investments, other investments	(139)	(549)
Net sales (purchases) of short-term securities	(176)	(108)
Securities transactions in course of settlement	87	150
Other investing activities	(144)	(135)
Net cash provided by (used in) investing activities	(621)	(459)
Dividends paid to parent company	(504)	(353)
Net cash used in financing activities	(504)	(353)
Net increase in cash	(4)	(1)
Cash at beginning of year	114	86
Cash at end of period	110	85
Income taxes paid (received)	286	199
Interest paid	36	36
Other Subsidiaries [Member]
Net income	394	43
Net adjustments to reconcile net income to net cash provided by operating activities	(283)	99
Net cash provided by operating activities	111	142
Proceeds from maturities of fixed maturities	1,350	1,265
Proceeds from sales of investments, fixed maturities	173	353
Proceeds from sales of investments, equity securities	7	32
Proceeds from sales of investments, real estate investments	3
Proceeds from sales of investments, other investments	89	102
Purchases of investments, fixed maturities	(1,454)	(1,204)
Purchases of investments, equity securities	(30)	(74)
Purchases of investments, real estate investments	(58)	(11)
Purchases of investments, other investments	(82)	(80)
Net sales (purchases) of short-term securities	115	(500)
Securities transactions in course of settlement	(10)	63
Other investing activities	11	(8)
Net cash provided by (used in) investing activities	114	(62)
Payment of debt		(8)
Dividends paid to parent company	(208)
Net cash used in financing activities	(208)	(8)
Effect of exchange rate changes on cash	1	4
Net increase in cash	18	76
Cash at beginning of year	98	110
Cash at end of period	116	186
Income taxes paid (received)	113	114
Travelers [Member]
Net income	1,305	475
Net adjustments to reconcile net income to net cash provided by operating activities	(560)	(174)
Net cash provided by operating activities	745	301
Proceeds from sales of investments, fixed maturities	1	1
Purchases of investments, fixed maturities	(2)	(1)
Purchases of investments, equity securities	(1)	(29)
Net sales (purchases) of short-term securities	428	1,205
Net cash provided by (used in) investing activities	426	1,176
Payment of debt	(258)
Dividends paid to shareholders	(341)	(329)
Issuance of common stock - employee share options	170	245
Treasury shares acquired - share repurchase authorization	(707)	(1,360)
Treasury shares acquired - net employee share-based compensation	(52)	(46)
Excess tax benefits from share-based payment arrangements	19	11
Net cash used in financing activities	(1,169)	(1,479)
Net increase in cash	2	(2)
Cash at beginning of year	2	4
Cash at end of period	4	2
Income taxes paid (received)	(103)	(22)
Interest paid	155	155
Eliminations [Member]
Net income	(1,406)	(499)
Net adjustments to reconcile net income to net cash provided by operating activities	694	146
Net cash provided by operating activities	(712)	(353)
Dividends paid to parent company	712	353
Net cash used in financing activities	$ 712	$ 353