Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Condensed Statement of Income Captions [Line Items]
Net premiums written	$ 8,343	$ 8,015	$ 15,656	$ 15,119
Net premiums earned	7,891	7,664	15,028	14,691
Net investment income	859	828	1,695	1,634
Equity In Earnings Of Subsidiaries	0	0	0	0
Net Realized Gains Losses	(223)	18	(320)	16
Losses and loss expenses	4,715	4,487	8,813	8,589
Policy benefits	161	150	357	301
Policy acquisition costs and administrative expenses	2,302	2,211	4,476	4,367
Interest (income) expense	140	167	280	324
Other (income) expense	(230)	(115)	(269)	(162)
Amortization of purchased intangibles	77	85	153	170
Chubb integration expenses	4	13	7	23
Income tax expense	208	218	396	353
Net income	1,150	1,294	2,190	2,376
Comprehensive income (loss)	2,059	277	4,777	730
Consolidating Adjustments and Eliminations
Condensed Statement of Income Captions [Line Items]
Net premiums written	0	0	0	0
Net premiums earned	0	0	0	0
Net investment income	0	0	0	0
Equity In Earnings Of Subsidiaries	(1,866)	(1,695)	(3,615)	(3,602)
Net Realized Gains Losses	0	0	0	0
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	0	0	0	0
Interest (income) expense	0	0	0	0
Other (income) expense	0	0	0	0
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses	0	0	0	0
Income tax expense	0	0	0	0
Net income	(1,866)	(1,695)	(3,615)	(3,602)
Comprehensive income (loss)	(3,578)	110	(8,307)	(720)
Chubb Limited (Parent Guarantor)
Condensed Statement of Income Captions [Line Items]
Net premiums written	0	0	0	0
Net premiums earned	0	0	0	0
Net investment income	1	1	2	3
Equity In Earnings Of Subsidiaries	1,104	1,241	2,094	2,263
Net Realized Gains Losses	4	2	5	0
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	22	23	42	41
Interest (income) expense	(62)	(76)	(128)	(156)
Other (income) expense	(6)	(4)	(12)	(9)
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses	0	2	0	4
Income tax expense	5	5	9	10
Net income	1,150	1,294	2,190	2,376
Comprehensive income (loss)	2,059	277	4,777	730
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Statement of Income Captions [Line Items]
Net premiums written	0	0	0	0
Net premiums earned	0	0	0	0
Net investment income	(6)	5	(10)	9
Equity In Earnings Of Subsidiaries	762	454	1,521	1,339
Net Realized Gains Losses	(21)	73	(34)	49
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	(5)	19	(20)	41
Interest (income) expense	180	204	365	413
Other (income) expense	1	8	4	16
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses	0	0	2	1
Income tax expense	(45)	(36)	(87)	(95)
Net income	604	337	1,213	1,021
Comprehensive income (loss)	1,397	(462)	3,338	(246)
Other Chubb Limited Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net premiums written	8,343	8,015	15,656	15,119
Net premiums earned	7,891	7,664	15,028	14,691
Net investment income	864	822	1,703	1,622
Equity In Earnings Of Subsidiaries	0	0	0	0
Net Realized Gains Losses	(206)	(57)	(291)	(33)
Losses and loss expenses	4,715	4,487	8,813	8,589
Policy benefits	161	150	357	301
Policy acquisition costs and administrative expenses	2,285	2,169	4,454	4,285
Interest (income) expense	22	39	43	67
Other (income) expense	(225)	(119)	(261)	(169)
Amortization of purchased intangibles	77	85	153	170
Chubb integration expenses	4	11	5	18
Income tax expense	248	249	474	438
Net income	1,262	1,358	2,402	2,581
Comprehensive income (loss)	$ 2,181	$ 352	$ 4,969	$ 966