Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Consolidating Statement of Cash Flows
Net income	$ 833	$ 1,052
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	(634)	(349)
Net cash provided by operating activities	199	703
Proceeds from maturities of fixed maturities	2,830	2,312
Proceeds from sales of investments, fixed maturities	906	406
Proceeds from sales of investments, equity securities	11	36
Proceeds from sales of investments, real estate investments	7	1
Proceeds from sales of investments, other investments	146	167
Purchases of investments, fixed maturities	(3,325)	(2,715)
Purchases of investments, equity securities	(8)	(18)
Purchases of investments, real estate investments	(6)	(9)
Purchases of investments, other investments	(168)	(113)
Net (purchases) sales of short-term securities	(134)	(160)
Securities transactions in course of settlement	305	240
Acquisition, net of cash acquired		(12)
Other investing activities	(90)	(60)
Net cash provided by investing activities	474	75
Treasury stock acquired - share repurchase authorization	(600)	(650)
Treasury stock acquired - net employee share-based compensation	(71)	(54)
Dividends paid to shareholders	(177)	(176)
Issuance of common stock - employee share options	90	57
Excess tax benefits from share-based payment arrangements	27	13
Net cash used in financing activities	(731)	(810)
Effect of exchange rate changes on cash	(8)	(2)
Net decrease in cash	(66)	(34)
Cash at beginning of year	374	294
Cash at end of period	308	260
Income taxes paid (received)	126	93
Interest paid	34	34
Reportable Legal Entities [Member] | TPC [Member]
Consolidating Statement of Cash Flows
Net income	632	783
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	(405)	(90)
Net cash provided by operating activities	227	693
Proceeds from maturities of fixed maturities	1,851	1,334
Proceeds from sales of investments, fixed maturities	555	192
Proceeds from sales of investments, equity securities	6	22
Proceeds from sales of investments, other investments	98	100
Purchases of investments, fixed maturities	(2,133)	(1,681)
Purchases of investments, equity securities	(1)	(1)
Purchases of investments, other investments	(139)	(74)
Net (purchases) sales of short-term securities	(23)	(73)
Securities transactions in course of settlement	175	183
Acquisition, net of cash acquired		(9)
Other investing activities	(89)	(58)
Net cash provided by investing activities	300	(65)
Dividends paid to parent company	(552)	(625)
Net cash used in financing activities	(552)	(625)
Effect of exchange rate changes on cash	(1)	(1)
Net decrease in cash	(26)	2
Cash at beginning of year	221	137
Cash at end of period	195	139
Income taxes paid (received)	138	64
Interest paid	16	16
Reportable Legal Entities [Member] | Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income	255	321
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	(350)	(315)
Net cash provided by operating activities	(95)	6
Proceeds from maturities of fixed maturities	979	977
Proceeds from sales of investments, fixed maturities	351	214
Proceeds from sales of investments, equity securities	5	10
Proceeds from sales of investments, real estate investments	7	1
Proceeds from sales of investments, other investments	48	67
Purchases of investments, fixed maturities	(1,192)	(1,030)
Purchases of investments, equity securities	(6)	(13)
Purchases of investments, real estate investments	(6)	(9)
Purchases of investments, other investments	(29)	(39)
Net (purchases) sales of short-term securities	6	(37)
Securities transactions in course of settlement	130	56
Acquisition, net of cash acquired		(3)
Other investing activities	(1)	(2)
Net cash provided by investing activities	292	192
Dividends paid to parent company	(230)	(232)
Net cash used in financing activities	(230)	(232)
Effect of exchange rate changes on cash	(7)	(1)
Net decrease in cash	(40)	(35)
Cash at beginning of year	151	154
Cash at end of period	111	119
Income taxes paid (received)	52	15
Reportable Legal Entities [Member] | Travelers [Member]
Consolidating Statement of Cash Flows
Net income	833	1,052
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	16	(191)
Net cash provided by operating activities	849	861
Proceeds from maturities of fixed maturities		1
Proceeds from sales of investments, equity securities		4
Purchases of investments, fixed maturities		(4)
Purchases of investments, equity securities	(1)	(4)
Net (purchases) sales of short-term securities	(117)	(50)
Securities transactions in course of settlement		1
Net cash provided by investing activities	(118)	(52)
Treasury stock acquired - share repurchase authorization	(600)	(650)
Treasury stock acquired - net employee share-based compensation	(71)	(54)
Dividends paid to shareholders	(177)	(176)
Issuance of common stock - employee share options	90	57
Excess tax benefits from share-based payment arrangements	27	13
Net cash used in financing activities	(731)	(810)
Net decrease in cash		(1)
Cash at beginning of year	2	3
Cash at end of period	2	2
Income taxes paid (received)	(64)	14
Interest paid	18	18
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income	(887)	(1,104)
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	105	247
Net cash provided by operating activities	(782)	(857)
Dividends paid to parent company	782	857
Net cash used in financing activities	$ 782	$ 857