Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Statement of Income Captions [Line Items]
Net premiums written	$ 7,104	$ 6,710
Net premiums earned	7,027	6,772
Net investment income	806	745
Income (Loss) from Subsidiaries, Net of Tax	0	0
Net realized gains (losses) including OTTI	(2)	(7)
Losses and loss expenses	4,102	3,789
Policy benefits	151	168
Policy acquisition costs and administrative expenses	2,156	2,073
Interest (income) expense	157	154
Other (income) expense	(47)	(70)
Amortization of purchased intangibles	85	64
Chubb integration expenses	10	111
Income tax expense	135	128
Net income	1,082	1,093
Comprehensive income (loss)	453	1,407
Consolidating Adjustments and Eliminations
Condensed Statement of Income Captions [Line Items]
Net premiums written	0	0
Net premiums earned	0	0
Net investment income	0	0
Income (Loss) from Subsidiaries, Net of Tax	(1,907)	(1,728)
Net realized gains (losses) including OTTI	0	0
Losses and loss expenses	0	0
Policy benefits	0	0
Policy acquisition costs and administrative expenses	0	0
Interest (income) expense	0	0
Other (income) expense	0	0
Amortization of purchased intangibles	0	0
Chubb integration expenses	0	0
Income tax expense	0	0
Net income	(1,907)	(1,728)
Comprehensive income (loss)	(830)	(2,329)
Chubb Limited (Parent Guarantor)
Condensed Statement of Income Captions [Line Items]
Net premiums written	0	0
Net premiums earned	0	0
Net investment income	2	0
Income (Loss) from Subsidiaries, Net of Tax	1,022	1,027
Net realized gains (losses) including OTTI	(2)	0
Losses and loss expenses	0	0
Policy benefits	0	0
Policy acquisition costs and administrative expenses	18	18
Interest (income) expense	(80)	(84)
Other (income) expense	(5)	(6)
Amortization of purchased intangibles	0	0
Chubb integration expenses	2	0
Income tax expense	5	6
Net income	1,082	1,093
Comprehensive income (loss)	453	1,407
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Statement of Income Captions [Line Items]
Net premiums written	0	0
Net premiums earned	0	0
Net investment income	4	3
Income (Loss) from Subsidiaries, Net of Tax	885	701
Net realized gains (losses) including OTTI	(24)	(13)
Losses and loss expenses	0	0
Policy benefits	0	0
Policy acquisition costs and administrative expenses	22	14
Interest (income) expense	209	221
Other (income) expense	8	15
Amortization of purchased intangibles	0	0
Chubb integration expenses	1	49
Income tax expense	(59)	(112)
Net income	684	504
Comprehensive income (loss)	216	791
Other Chubb Limited Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net premiums written	7,104	6,710
Net premiums earned	7,027	6,772
Net investment income	800	742
Income (Loss) from Subsidiaries, Net of Tax	0	0
Net realized gains (losses) including OTTI	24	6
Losses and loss expenses	4,102	3,789
Policy benefits	151	168
Policy acquisition costs and administrative expenses	2,116	2,041
Interest (income) expense	28	17
Other (income) expense	(50)	(79)
Amortization of purchased intangibles	85	64
Chubb integration expenses	7	62
Income tax expense	189	234
Net income	1,223	1,224
Comprehensive income (loss)	$ 614	$ 1,538