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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net Realized Gain (Loss)	$ (687)	$ 19	$ 18	$ (2)					$ (652)
Net premiums written									30,579	$ 29,244	$ 28,145
Net premiums earned	7,465	7,908	7,664	7,027	$ 7,218	$ 7,807	$ 7,237	$ 6,772	30,064	29,034	28,749
Net Investment Income	848	823	828	806	797	813	770	745	3,305	3,125	2,865
Equity in earnings of subsidiaries									0	0	0
Realized Gain (Loss) on Marketable Securities, Cost Method Investments, and Other Investments						(10)	101	(7)		84	(145)
Losses and loss expenses	4,610	4,868	4,487	4,102	4,272	6,247	4,146	3,789	18,067	18,454	16,052
Policy benefits	162	127	150	151	176	169	163	168	590	676	588
Policy acquisition costs and administrative expenses									8,798	8,614	8,985
Interest (income) expense									641	607	605
Other (Income) Expense									(434)	(400)	(222)
Amortization of Purchased Intangibles									339	260	19
Chubb integration expenses									59	310	492
Income tax expense (benefit)									695	(139)	815
Net income	$ 355	$ 1,231	$ 1,294	$ 1,082	$ 1,533	$ (70)	$ 1,305	$ 1,093	3,962	3,861	4,135
Comprehensive income									1,242
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									6	4	3
Equity in earnings of subsidiaries									3,753	3,640	3,901
Losses and loss expenses									0	0	0
Policy benefits									0	0	0
Policy acquisition costs and administrative expenses									87	75	64
Interest (income) expense									(299)	(332)	(353)
Other (Income) Expense									(24)	(12)	(25)
Amortization of Purchased Intangibles									0	0	0
Chubb integration expenses									14	32	62
Income tax expense (benefit)									19	20	21
Net income									3,962	3,861	4,135
Comprehensive income									1,242	4,718	4,556
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net Realized Gain (Loss)									117
Net premiums written									0	0	0
Net premiums earned									0	0	0
Net Investment Income									13	14	11
Equity in earnings of subsidiaries									2,578	2,424	2,555
Realized Gain (Loss) on Marketable Securities, Cost Method Investments, and Other Investments										(25)	3
Losses and loss expenses									0	0	0
Policy benefits									0	0	0
Policy acquisition costs and administrative expenses									(58)	40	82
Interest (income) expense									806	847	908
Other (Income) Expense									26	93	35
Amortization of Purchased Intangibles									0	0	0
Chubb integration expenses									1	69	126
Income tax expense (benefit)									(148)	(742)	(416)
Net income									2,081	2,106	1,834
Comprehensive income									(27)	3,075	2,001
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net Realized Gain (Loss)									(769)
Net premiums written									30,579	29,244	28,145
Net premiums earned									30,064	29,034	28,749
Net Investment Income									3,286	3,107	2,851
Equity in earnings of subsidiaries									0	0	0
Realized Gain (Loss) on Marketable Securities, Cost Method Investments, and Other Investments										109	(148)
Losses and loss expenses									18,067	18,454	16,052
Policy benefits									590	676	588
Policy acquisition costs and administrative expenses									8,769	8,499	8,839
Interest (income) expense									134	92	50
Other (Income) Expense									(436)	(481)	(232)
Amortization of Purchased Intangibles									339	260	19
Chubb integration expenses									44	209	304
Income tax expense (benefit)									824	583	1,210
Net income									4,250	3,958	4,622
Comprehensive income									1,808	4,430	5,045
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									(6,331)	(6,064)	(6,456)
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									(6,331)	(6,064)	(6,456)
Comprehensive income									$ (1,781)	$ (7,505)	$ (7,046)