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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Condensed Statement of Income Captions [Line Items]
Net premiums written	$ 8,355	$ 8,343	$ 16,332	$ 15,656
Net premiums earned	8,128	7,891	15,922	15,028
Net investment income	827	859	1,688	1,695
Equity In Earnings Of Subsidiaries	0	0	0	0
Net Realized Gains Losses	30	(223)	(928)	(320)
Losses and loss expenses	6,577	4,715	11,062	8,813
Policy benefits	223	161	352	357
Policy acquisition costs and administrative expenses	2,320	2,302	4,676	4,476
Interest (income) expense	128	140	260	280
Other (income) expense	58	(230)	113	(269)
Amortization of purchased intangibles	72	77	145	153
Chubb integration expenses	0	4	0	7
Income tax benefit	(62)	208	153	396
Net income (loss)	(331)	1,150	(79)	2,190
Comprehensive income (loss)	2,860	2,059	400	4,777
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	0	1	(2)	2
Equity In Earnings Of Subsidiaries	(366)	1,104	(110)	2,094
Net Realized Gains Losses	23	4	2	5
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	21	22	45	42
Interest (income) expense	(35)	(62)	(69)	(128)
Other (income) expense	(8)	(6)	(17)	(12)
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses		0		0
Income tax benefit	10	5	10	9
Net income (loss)	(331)	1,150	(79)	2,190
Comprehensive income (loss)	2,860	2,059	400	4,777
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	1	(6)	5	(10)
Equity In Earnings Of Subsidiaries	(271)	762	322	1,521
Net Realized Gains Losses	(192)	(21)	(79)	(34)
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	(30)	(5)	(68)	(20)
Interest (income) expense	149	180	297	365
Other (income) expense	(5)	1	3	4
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses		0		2
Income tax benefit	(66)	(45)	(59)	(87)
Net income (loss)	(510)	604	75	1,213
Comprehensive income (loss)	1,872	1,397	672	3,338
Other Chubb Limited Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net premiums written	8,355	8,343	16,332	15,656
Net premiums earned	8,128	7,891	15,922	15,028
Net investment income	826	864	1,685	1,703
Equity In Earnings Of Subsidiaries	0	0	0	0
Net Realized Gains Losses	199	(206)	(851)	(291)
Losses and loss expenses	6,577	4,715	11,062	8,813
Policy benefits	223	161	352	357
Policy acquisition costs and administrative expenses	2,329	2,285	4,699	4,454
Interest (income) expense	14	22	32	43
Other (income) expense	71	(225)	127	(261)
Amortization of purchased intangibles	72	77	145	153
Chubb integration expenses		4		5
Income tax benefit	(6)	248	202	474
Net income (loss)	(127)	1,262	137	2,402
Comprehensive income (loss)	3,078	2,181	660	4,969
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	637	(1,866)	(212)	(3,615)
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
Income tax benefit	0	0	0	0
Net income (loss)	637	(1,866)	(212)	(3,615)
Comprehensive income (loss)	$ (4,950)	$ (3,578)	$ (1,332)	$ (8,307)