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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Statement of Income Captions [Line Items]
Net premiums written	$ 8,015	$ 7,581	$ 15,119	$ 14,291
Net premiums earned	7,664	7,237	14,691	14,009
Net investment income	828	770	1,634	1,515
Income (Loss) from Subsidiaries, Net of Tax	0	0	0	0
Net realized gains (losses) including OTTI	18	101	16	94
Losses and loss expenses	4,487	4,146	8,589	7,935
Policy benefits	150	163	301	331
Policy acquisition costs and administrative expenses	2,211	2,155	4,367	4,228
Interest (income) expense	167	147	324	301
Other (income) expense	(115)	(145)	(162)	(215)
Amortization of purchased intangibles	85	65	170	129
Chubb integration expenses	13	72	23	183
Income tax expense	218	200	353	328
Net income	1,294	1,305	2,376	2,398
Comprehensive income (loss)	277	1,675	730	3,082
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
Income (Loss) from Subsidiaries, Net of Tax	(1,695)	(1,918)	(3,602)	(3,646)
Net realized gains (losses) including OTTI	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	(1,695)	(1,918)	(3,602)	(3,646)
Comprehensive income (loss)	110	(2,676)	(720)	(5,005)
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	2
Income (Loss) from Subsidiaries, Net of Tax	1,241	1,253	2,263	2,280
Net realized gains (losses) including OTTI	2	(2)	0	(2)
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	23	18	41	36
Interest (income) expense	(76)	(84)	(156)	(168)
Other (income) expense	(4)	4	(9)	(2)
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses	2	6	4	6
Income tax expense	5	4	10	10
Net income	1,294	1,305	2,376	2,398
Comprehensive income (loss)	277	1,675	730	3,082
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	5	4	9	7
Income (Loss) from Subsidiaries, Net of Tax	454	665	1,339	1,366
Net realized gains (losses) including OTTI	73	(1)	49	(14)
Losses and loss expenses	0	0	0	0
Policy benefits	0	0	0	0
Policy acquisition costs and administrative expenses	19	(2)	41	12
Interest (income) expense	204	212	413	433
Other (income) expense	8	10	16	25
Amortization of purchased intangibles	0	0	0	0
Chubb integration expenses	0	4	1	53
Income tax expense	(36)	(87)	(95)	(199)
Net income	337	531	1,021	1,035
Comprehensive income (loss)	(462)	920	(246)	1,711
Other Chubb Limited Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net premiums written	8,015	7,581	15,119	14,291
Net premiums earned	7,664	7,237	14,691	14,009
Net investment income	822	764	1,622	1,506
Income (Loss) from Subsidiaries, Net of Tax	0	0	0	0
Net realized gains (losses) including OTTI	(57)	104	(33)	110
Losses and loss expenses	4,487	4,146	8,589	7,935
Policy benefits	150	163	301	331
Policy acquisition costs and administrative expenses	2,169	2,139	4,285	4,180
Interest (income) expense	39	19	67	36
Other (income) expense	(119)	(159)	(169)	(238)
Amortization of purchased intangibles	85	65	170	129
Chubb integration expenses	11	62	18	124
Income tax expense	249	283	438	517
Net income	1,358	1,387	2,581	2,611
Comprehensive income (loss)	$ 352	$ 1,756	$ 966	$ 3,294