Schedule II (Details) - Condensed Income Statement - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Statement of Income
Net investment income										$ 2,474	$ 2,397	$ 2,302
Net realized investment gains (losses)	[1]									114	216	68
Total revenues		$ 7,796	$ 7,723	$ 7,477	$ 7,286	$ 7,451	$ 7,325	$ 7,184	$ 6,942	30,282	28,902	27,625
Interest expense										352	369	363
Expenses, other										4,297	4,170	4,154
Total claims and expenses		7,050	6,917	6,846	6,508	6,591	7,005	6,394	6,182	27,321	26,172	23,572
Income before income taxes		746	806	631	778	860	320	790	760	2,961	2,730	4,053
Income tax expense (benefit)		125	97	107	109	309	27	195	143	438	674	1,039
Net income		$ 621	$ 709	$ 524	$ 669	$ 551	$ 293	$ 595	$ 617	2,523	2,056	3,014
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										(1)
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											(14)	(29)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)										0		(11)
Other-than-temporary impairment gains recognized in other comprehensive income (loss)											1
Travelers [Member]
Condensed Statement of Income
Net investment income										32	24	13
Net realized investment gains (losses)										(13)	66	(1)
Total revenues										19	90	12
Interest expense										304	321	315
Expenses, other										20	25	5
Total claims and expenses										324	346	320
Income before income taxes										(305)	(256)	(308)
Income tax expense (benefit)										(114)	(130)	(168)
Loss before net income of subsidiaries										(191)	(126)	(140)
Net income of subsidiaries										2,714	2,190	3,154
Net income										2,523	2,064	3,014
Other-than-temporary impairment losses recognized in net realized investment gains (losses)										0
Other-than-temporary impairment losses recognized in net realized investment gains (losses)											0	(1)
Other-than-temporary impairment losses recognized in other comprehensive income (loss)										$ 0		$ 0
Other-than-temporary impairment gains recognized in other comprehensive income (loss)											$ 0

[1] Total other-than-temporary impairment (OTTI) losses were $(1) million, $(13) million and $(40) million for the years ended December 31, 2018, 2017 and 2016, respectively. Of total OTTI, credit losses of $(1) million, $(14) million and $(29) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $0 million, $1 million and $(11) million for the years ended December 31, 2018, 2017 and 2016, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains (losses) on investment securities having credit losses recognized in the consolidated statement of income.