Investments (Schedule Of Sources Of Net Investment Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Investment Income [Line Items]
Gross investment income	$ 3,551	$ 3,598	$ 3,473
Investment expenses	(176)	(172)	(168)
Net investment income	3,375	3,426	3,305
Amortization of Debt Issuance Costs and Discounts	(367)	(395)	(592)
The Chubb Corporation [Member]
Net Investment Income [Line Items]
Amortization of Debt Issuance Costs and Discounts	(116)	(161)	(248)
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross investment income	3,321	3,385	3,128
Short-term investments
Net Investment Income [Line Items]
Gross investment income	48	84	90
Other interest income [Member]
Net Investment Income [Line Items]
Gross investment income	19	25	118
Equity securities
Net Investment Income [Line Items]
Gross investment income	81	26	33
Other Investments [Member]
Net Investment Income [Line Items]
Gross investment income	$ 82	$ 78	$ 104