Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Consolidating Financial Statements, Captions
Net income	$ 2,169	$ 808
Net adjustments to reconcile net income to net cash provided by operating activities	597	1,010
Net cash provided by operating activities	2,766	1,818
Proceeds from maturities of fixed maturities	5,855	5,241
Proceeds from sales of investments, fixed maturities	724	842
Proceeds from sales of investments, equity securities	31	51
Proceeds from sales of investments, real estate investments	3	1
Proceeds from sales of investments, other investments	516	482
Purchases of investments, fixed maturities	(7,677)	(6,224)
Purchases of investments, equity securities	(39)	(118)
Purchases of investments, real estate investments	(62)	(41)
Purchases of investments, other investments	(292)	(758)
Net sales (purchases) of short-term securities	(41)	813
Securities transactions in course of settlement	53	196
Other investing activities	(229)	(248)
Net cash provided by (used in) investing activities	(1,158)	237
Payment of debt	(258)	(8)
Dividends paid to shareholders	(519)	(500)
Issuance of common stock - employee share options	247	270
Treasury shares acquired - share repurchase authorization	(1,056)	(1,755)
Treasury shares acquired - net employee share-based compensation	(52)	(46)
Excess tax benefits from share-based payment arrangements	32	17
Net cash used in financing activities	(1,606)	(2,022)
Effect of exchange rate changes on cash	4	(2)
Net increase in cash	6	31
Cash at beginning of year	214	200
Cash at end of period	220	231
Income taxes paid (received)	310	277
Interest paid	226	226
TPC [Member]
Consolidating Financial Statements, Captions
Net income	1,610	710
Net adjustments to reconcile net income to net cash provided by operating activities	552	764
Net cash provided by operating activities	2,162	1,474
Proceeds from maturities of fixed maturities	4,123	3,490
Proceeds from sales of investments, fixed maturities	494	452
Proceeds from sales of investments, equity securities	18	15
Proceeds from sales of investments, real estate investments		1
Proceeds from sales of investments, other investments	389	301
Purchases of investments, fixed maturities	(5,645)	(4,131)
Purchases of investments, equity securities	(1)	(6)
Purchases of investments, real estate investments		(24)
Purchases of investments, other investments	(187)	(622)
Net sales (purchases) of short-term securities	(306)	54
Securities transactions in course of settlement	46	128
Other investing activities	(235)	(234)
Net cash provided by (used in) investing activities	(1,304)	(576)
Dividends paid to parent company	(854)	(878)
Net cash used in financing activities	(854)	(878)
Net increase in cash	4	20
Cash at beginning of year	114	86
Cash at end of period	118	106
Income taxes paid (received)	343	221
Interest paid	65	65
Other Subsidiaries [Member]
Consolidating Financial Statements, Captions
Net income	704	173
Net adjustments to reconcile net income to net cash provided by operating activities	(136)	214
Net cash provided by operating activities	568	387
Proceeds from maturities of fixed maturities	1,731	1,751
Proceeds from sales of investments, fixed maturities	228	389
Proceeds from sales of investments, equity securities	13	36
Proceeds from sales of investments, real estate investments	3
Proceeds from sales of investments, other investments	127	181
Purchases of investments, fixed maturities	(2,023)	(2,092)
Purchases of investments, equity securities	(37)	(73)
Purchases of investments, real estate investments	(62)	(17)
Purchases of investments, other investments	(105)	(136)
Net sales (purchases) of short-term securities	(99)	(470)
Securities transactions in course of settlement	7	68
Other investing activities	6	(14)
Net cash provided by (used in) investing activities	(211)	(377)
Payment of debt		(8)
Dividends paid to parent company	(358)
Capital contributions, loans and other transactions between subsidiaries		10
Net cash used in financing activities	(358)	2
Effect of exchange rate changes on cash	4	(2)
Net increase in cash	3	10
Cash at beginning of year	98	110
Cash at end of period	101	120
Income taxes paid (received)	110	83
Travelers [Member]
Consolidating Financial Statements, Captions
Net income	2,169	808
Net adjustments to reconcile net income to net cash provided by operating activities	(921)	17
Net cash provided by operating activities	1,248	825
Proceeds from maturities of fixed maturities	1
Proceeds from sales of investments, fixed maturities	2	1
Purchases of investments, fixed maturities	(9)	(1)
Purchases of investments, equity securities	(1)	(39)
Net sales (purchases) of short-term securities	364	1,229
Net cash provided by (used in) investing activities	357	1,190
Payment of debt	(258)
Dividends paid to shareholders	(519)	(500)
Issuance of common stock - employee share options	247	270
Treasury shares acquired - share repurchase authorization	(1,056)	(1,755)
Treasury shares acquired - net employee share-based compensation	(52)	(46)
Excess tax benefits from share-based payment arrangements	32	17
Net cash used in financing activities	(1,606)	(2,014)
Net increase in cash	(1)	1
Cash at beginning of year	2	4
Cash at end of period	1	5
Income taxes paid (received)	(143)	(27)
Interest paid	161	161
Eliminations [Member]
Consolidating Financial Statements, Captions
Net income	(2,314)	(883)
Net adjustments to reconcile net income to net cash provided by operating activities	1,102	15
Net cash provided by operating activities	(1,212)	(868)
Dividends paid to parent company	1,212	878
Capital contributions, loans and other transactions between subsidiaries		(10)
Net cash used in financing activities	$ 1,212	$ 868