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Investments (Schedule Of Sources Of Net Investment Income) (Details) - 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
Net Investment Income [Line Items]
Gross investment income									$ 3,473	$ 3,289	$ 3,006
Investment expenses									(168)	(164)	(141)
Net investment income	$ 848	$ 823	$ 828	$ 806	$ 797	$ 813	$ 770	$ 745	3,305	3,125	2,865
Amortization of Debt Issuance Costs and Discounts									(592)	(694)	(737)
The Chubb Corporation [Member]
Net Investment Income [Line Items]
Amortization of Debt Issuance Costs and Discounts									(248)	(332)	(393)
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross investment income									3,128	2,987	2,779
Short-term investments
Net Investment Income [Line Items]
Gross investment income									90	56	58
Other interest income [Member]
Net Investment Income [Line Items]
Gross investment income									118	75	35
Equity securities
Net Investment Income [Line Items]
Gross investment income									33	38	36
Other Investments [Member]
Net Investment Income [Line Items]
Gross investment income									$ 104	$ 133	$ 98