Acquisitions (Acquisition operations) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Total revenues				$ 49,735	$ 43,097	$ 40,869
Net income				9,015	5,246	8,525
Net loss attributable to Chubb				$ 9,028	$ 5,246	$ 8,525
Huatai Group [Member]
Business Acquisition [Line Items]
Total revenues		$ 739
Net income		(30)
Net loss attributable to Chubb		$ (17)
Huatai Group [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Payments to Acquire Business and Interest in Affiliates, Pending	$ 221
Cigna's Life Insurance Business in Asian Markets
Business Acquisition [Line Items]
Total revenues			$ 1,507
Net loss attributable to Chubb			$ 140