Consolidating Financial Statements (details) - Consolidating Statement of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Consolidating Statement of Cash Flows
Net income	$ 691	$ 833
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	159	(634)
Net cash provided by operating activities	850	199
Proceeds from maturities of fixed maturities	1,748	2,830
Proceeds from sales of investments, fixed maturities	421	906
Proceeds from sales of investments, equity securities	14	11
Proceeds from sales of investments, real estate investments	69	7
Proceeds from sales of investments, other investments	186	146
Purchases of investments, fixed maturities	(2,700)	(3,325)
Purchases of investments, equity securities	(12)	(8)
Purchases of investments, real estate investments	(7)	(6)
Purchases of investments, other investments	(162)	(168)
Net sales (purchases) of short-term securities	85	(134)
Securities transactions in course of settlement	291	305
Other investing activities	(79)	(90)
Net cash provided by (used in) investing activities	(146)	474
Treasury stock acquired - share repurchase authorization	(550)	(600)
Treasury stock acquired - net employee share-based compensation	(59)	(71)
Dividends paid to shareholders	(180)	(177)
Issuance of common stock - employee share options	64	90
Excess tax benefits from share-based payment arrangements		27
Net cash used in financing activities	(725)	(731)
Effect of exchange rate changes on cash	2	(8)
Net decrease in cash	(19)	(66)
Cash at beginning of year	380	374
Cash at end of period	361	308
Income taxes paid (received)	63	126
Interest paid	42	34
TPC [Member]
Consolidating Statement of Cash Flows
Net income	525	632
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	151	(405)
Net cash provided by operating activities	676	227
Proceeds from maturities of fixed maturities	1,239	1,851
Proceeds from sales of investments, fixed maturities	237	555
Proceeds from sales of investments, equity securities	4	6
Proceeds from sales of investments, other investments	122	98
Purchases of investments, fixed maturities	(1,534)	(2,133)
Purchases of investments, equity securities	(1)	(1)
Purchases of investments, other investments	(123)	(139)
Net sales (purchases) of short-term securities	(152)	(23)
Securities transactions in course of settlement	159	175
Other investing activities	(78)	(89)
Net cash provided by (used in) investing activities	(127)	300
Dividends paid to parent company	(565)	(552)
Net cash used in financing activities	(565)	(552)
Effect of exchange rate changes on cash	2	(1)
Net decrease in cash	(14)	(26)
Cash at beginning of year	225	221
Cash at end of period	211	195
Income taxes paid (received)	51	138
Interest paid	16	16
Other Subsidiaries [Member]
Consolidating Statement of Cash Flows
Net income	205	255
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	(55)	(350)
Net cash provided by operating activities	150	(95)
Proceeds from maturities of fixed maturities	507	979
Proceeds from sales of investments, fixed maturities	183	351
Proceeds from sales of investments, equity securities	10	5
Proceeds from sales of investments, real estate investments	69	7
Proceeds from sales of investments, other investments	64	48
Purchases of investments, fixed maturities	(1,162)	(1,192)
Purchases of investments, equity securities	(10)	(6)
Purchases of investments, real estate investments	(7)	(6)
Purchases of investments, other investments	(39)	(29)
Net sales (purchases) of short-term securities	317	6
Securities transactions in course of settlement	131	130
Other investing activities	(1)	(1)
Net cash provided by (used in) investing activities	62	292
Dividends paid to parent company	(217)	(230)
Net cash used in financing activities	(217)	(230)
Effect of exchange rate changes on cash		(7)
Net decrease in cash	(5)	(40)
Cash at beginning of year	153	151
Cash at end of period	148	111
Income taxes paid (received)	17	52
Travelers [Member]
Consolidating Statement of Cash Flows
Net income	691	833
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	115	16
Net cash provided by operating activities	806	849
Proceeds from maturities of fixed maturities	2
Proceeds from sales of investments, fixed maturities	1
Purchases of investments, fixed maturities	(4)
Purchases of investments, equity securities	(1)	(1)
Net sales (purchases) of short-term securities	(80)	(117)
Securities transactions in course of settlement	1
Net cash provided by (used in) investing activities	(81)	(118)
Treasury stock acquired - share repurchase authorization	(550)	(600)
Treasury stock acquired - net employee share-based compensation	(59)	(71)
Dividends paid to shareholders	(180)	(177)
Issuance of common stock - employee share options	64	90
Excess tax benefits from share-based payment arrangements		27
Net cash used in financing activities	(725)	(731)
Cash at beginning of year	2	2
Cash at end of period	2	2
Income taxes paid (received)	(5)	(64)
Interest paid	26	18
Eliminations [Member]
Consolidating Statement of Cash Flows
Net income	(730)	(887)
Net adjustments to reconcile net income to net cash provided by (used in) operating activities	(52)	105
Net cash provided by operating activities	(782)	(782)
Dividends paid to parent company	782	782
Net cash used in financing activities	$ 782	$ 782