Investments (Schedule Of Sources Of Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Investment Income [Line Items]
Gross investment income									$ 3,598	$ 3,473	$ 3,289
Investment expenses									(172)	(168)	(164)
Net investment income	$ 858	$ 873	$ 859	$ 836	$ 848	$ 823	$ 828	$ 806	3,426	3,305	3,125
Amortization of Debt Issuance Costs and Discounts									(395)	(592)	(694)
The Chubb Corporation [Member]
Net Investment Income [Line Items]
Amortization of Debt Issuance Costs and Discounts									(161)	(248)	(332)
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross investment income									3,385	3,128	2,987
Short-term investments
Net Investment Income [Line Items]
Gross investment income									84	90	56
Other interest income [Member]
Net Investment Income [Line Items]
Gross investment income									25	118	75
Equity securities
Net Investment Income [Line Items]
Gross investment income									26	33	38
Other Investments [Member]
Net Investment Income [Line Items]
Gross investment income									$ 78	$ 104	$ 133