Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Statement of Income Captions [Line Items]
Net premiums written	$ 8,622	$ 8,110	$ 24,278	$ 23,229
Net premiums earned	8,327	7,908	23,355	22,599
Net investment income	873	823	2,568	2,457
Equity In Earnings Of Subsidiaries	0	0	0	0
Net Realized Gains Losses	(155)	19	(475)	35
Losses and loss expenses	5,052	4,868	13,865	13,457
Policy benefits	158	127	515	428
Policy acquisition costs and administrative expenses	2,355	2,223	6,831	6,590
Interest (income) expense	138	164	418	488
Other (income) expense	(57)	(145)	(326)	(307)
Amortization of purchased intangibles	76	83	229	253
Chubb integration expenses	2	16	9	39
Income tax expense	230	183	626	536
Net income	1,091	1,231	3,281	3,607
Comprehensive income (loss)	1,473	592	6,250	1,322
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	2	3	5
Equity In Earnings Of Subsidiaries	1,053	1,177	3,147	3,440
Net Realized Gains Losses	(4)	(1)	1	(1)
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	22	23	64	64
Interest (income) expense	(59)	(75)	(187)	(231)
Other (income) expense	(7)	(9)	(19)	(18)
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses	0	3	0	7
Income tax expense	3	5	12	15
Net income	1,091	1,231	3,281	3,607
Comprehensive income (loss)	1,473	592	6,250	1,322
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	(3)	3	(13)	12
Equity In Earnings Of Subsidiaries	824	709	2,345	2,048
Net Realized Gains Losses	68	18	34	67
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	(5)	(90)	(25)	(49)
Interest (income) expense	171	203	536	616
Other (income) expense	(3)	12	1	28
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses	0	1	2	2
Income tax expense	(33)	(24)	(120)	(119)
Net income	759	628	1,972	1,649
Comprehensive income (loss)	1,138	47	4,476	(199)
Other Chubb Limited Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net premiums written	8,622	8,110	24,278	23,229
Net premiums earned	8,327	7,908	23,355	22,599
Net investment income	875	818	2,578	2,440
Equity In Earnings Of Subsidiaries	0	0	0	0
Net Realized Gains Losses	(219)	2	(510)	(31)
Losses and loss expenses	5,052	4,868	13,865	13,457
Policy benefits	158	127	515	428
Policy acquisition costs and administrative expenses	2,338	2,290	6,792	6,575
Interest (income) expense	26	36	69	103
Other (income) expense	(47)	(148)	(308)	(317)
Amortization of purchased intangibles	76	83	229	253
Chubb integration expenses	2	12	7	30
Income tax expense	260	202	734	640
Net income	1,118	1,258	3,520	3,839
Comprehensive income (loss)	1,517	640	6,486	1,606
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	(1,877)	(1,886)	(5,492)	(5,488)
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	(1,877)	(1,886)	(5,492)	(5,488)
Comprehensive income (loss)	$ (2,655)	$ (687)	$ (10,962)	$ (1,407)