Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed Statement of Income Captions [Line Items]
Net premiums written	$ 7,313	$ 7,104
Net premiums earned	7,137	7,027
Net investment income	836	806
Equity In Earnings Of Subsidiaries	0	0
Net Realized Gains Losses	(97)	(2)
Losses and loss expenses	4,098	4,102
Policy benefits	196	151
Policy acquisition costs and administrative expenses	2,174	2,156
Interest (income) expense	140	157
Other (income) expense	(39)	(47)
Amortization of purchased intangibles	76	85
Chubb integration expenses	3	10
Income tax expense	188	135
Net income	1,040	1,082
Comprehensive income (loss)	2,718	453
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
Equity In Earnings Of Subsidiaries	(1,749)	(1,907)
Net Realized Gains Losses	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	(1,749)	(1,907)
Comprehensive income (loss)	(4,729)	(830)
Chubb Limited (Parent Guarantor)
Condensed Statement of Income Captions [Line Items]
Net premiums written	0	0
Net premiums earned	0	0
Net investment income	1	2
Equity In Earnings Of Subsidiaries	990	1,022
Net Realized Gains Losses	1	(2)
Losses and loss expenses	0	0
Policy benefits	0	0
Policy acquisition costs and administrative expenses	20	18
Interest (income) expense	(66)	(80)
Other (income) expense	(6)	(5)
Amortization of purchased intangibles	0	0
Chubb integration expenses	0	2
Income tax expense	4	5
Net income	1,040	1,082
Comprehensive income (loss)	2,718	453
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)	4
Equity In Earnings Of Subsidiaries	759	885
Net Realized Gains Losses	(13)	(24)
Losses and loss expenses	0	0
Policy benefits	0	0
Policy acquisition costs and administrative expenses	(15)	22
Interest (income) expense	185	209
Other (income) expense	3	8
Amortization of purchased intangibles	0	0
Chubb integration expenses	2	1
Income tax expense	(42)	(59)
Net income	609	684
Comprehensive income (loss)	1,941	216
Other Chubb Limited Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net premiums written	7,313	7,104
Net premiums earned	7,137	7,027
Net investment income	839	800
Equity In Earnings Of Subsidiaries	0	0
Net Realized Gains Losses	(85)	24
Losses and loss expenses	4,098	4,102
Policy benefits	196	151
Policy acquisition costs and administrative expenses	2,169	2,116
Interest (income) expense	21	28
Other (income) expense	(36)	(50)
Amortization of purchased intangibles	76	85
Chubb integration expenses	1	7
Income tax expense	226	189
Net income	1,140	1,223
Comprehensive income (loss)	$ 2,788	$ 614