Shareholders' equity AOCI Reclassifications (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 741	$ 672	$ 570
Income tax expense	1,815	511	1,239
Net income attributable to Chubb	9,272	9,028	5,246
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income attributable to Chubb	(288)	(401)	(797)
Reclassification out of Accumulated Other Comprehensive Income [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	92	62	170
Net income attributable to Chubb	(210)	(438)	(879)
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	(302)	(500)	(1,049)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cumulative Translation Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	19	13	4
Income tax expense	(4)	(3)	(1)
Net income attributable to Chubb	15	10	3
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Foreign Currency Transaction Gain (Loss), Realized	(103)	50	105
Interest expense	(15)	(16)	(5)
Income tax expense	25	(7)	(21)
Net income attributable to Chubb	$ (93)	$ 27	$ 79