Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Statement Of Operations and Comprehensive Income) (Detail) - 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
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written									$ 32,275	$ 30,579	$ 29,244
Net premiums earned	$ 7,935	$ 8,327	$ 7,891	$ 7,137	$ 7,465	$ 7,908	$ 7,664	$ 7,027	31,290	30,064	29,034
Net Investment Income	858	873	859	836	848	823	828	806	3,426	3,305	3,125
Equity in earnings of subsidiaries									0	0	0
Net Realized Gains Losses	(55)	(155)	(223)	(97)	(687)	19	18	(2)	(530)	(652)	84
Losses and loss expenses	4,865	5,052	4,715	4,098	4,610	4,868	4,487	4,102	18,730	18,067	18,454
Policy benefits	225	158	161	196	162	127	150	151	740	590	676
Policy acquisition costs and administrative expenses									9,183	8,798	8,614
Interest (income) expense									552	641	607
Other (Income) Expense									(596)	(434)	(400)
Amortization of Purchased Intangibles									305	339	260
Chubb integration expenses									23	59	310
Income tax expense (benefit)									795	695	(139)
Net income	$ 1,173	$ 1,091	$ 1,150	$ 1,040	$ 355	$ 1,231	$ 1,294	$ 1,082	4,454	3,962	3,861
Comprehensive income									7,521	1,242	4,718
Chubb limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written									0	0	0
Net premiums earned									0	0	0
Net Investment Income									1	6	4
Equity in earnings of subsidiaries									4,307	3,753	3,640
Net Realized Gains Losses									(17)	0	0
Losses and loss expenses									0	0	0
Policy benefits									0	0	0
Policy acquisition costs and administrative expenses									92	87	75
Interest (income) expense									(243)	(299)	(332)
Other (Income) Expense									(27)	(24)	(12)
Amortization of Purchased Intangibles									0	0	0
Chubb integration expenses									1	14	32
Income tax expense (benefit)									14	19	20
Net income									4,454	3,962	3,861
Comprehensive income									7,521	1,242	4,718
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written									0	0	0
Net premiums earned									0	0	0
Net Investment Income									(15)	13	14
Equity in earnings of subsidiaries									3,022	2,578	2,424
Net Realized Gains Losses									(31)	117	(25)
Losses and loss expenses									0	0	0
Policy benefits									0	0	0
Policy acquisition costs and administrative expenses									(26)	(58)	40
Interest (income) expense									705	806	847
Other (Income) Expense									6	26	93
Amortization of Purchased Intangibles									0	0	0
Chubb integration expenses									2	1	69
Income tax expense (benefit)									(175)	(148)	(742)
Net income									2,464	2,081	2,106
Comprehensive income									4,988	(27)	3,075
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written									32,275	30,579	29,244
Net premiums earned									31,290	30,064	29,034
Net Investment Income									3,440	3,286	3,107
Equity in earnings of subsidiaries									0	0	0
Net Realized Gains Losses									(482)	(769)	109
Losses and loss expenses									18,730	18,067	18,454
Policy benefits									740	590	676
Policy acquisition costs and administrative expenses									9,117	8,769	8,499
Interest (income) expense									90	134	92
Other (Income) Expense									(575)	(436)	(481)
Amortization of Purchased Intangibles									305	339	260
Chubb integration expenses									20	44	209
Income tax expense (benefit)									956	824	583
Net income									4,865	4,250	3,958
Comprehensive income									7,922	1,808	4,430
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net premiums written									0	0	0
Net premiums earned									0	0	0
Net Investment Income									0	0	0
Equity in earnings of subsidiaries									(7,329)	(6,331)	(6,064)
Net Realized Gains Losses									0	0	0
Losses and loss expenses									0	0	0
Policy benefits									0	0	0
Policy acquisition costs and administrative expenses									0	0	0
Interest (income) expense									0	0	0
Other (Income) Expense									0	0	0
Amortization of Purchased Intangibles										0	0
Chubb integration expenses									0	0	0
Income tax expense (benefit)									0	0	0
Net income									(7,329)	(6,331)	(6,064)
Comprehensive income									$ (12,910)	$ (1,781)	$ (7,505)