Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Condensed Statement of Income Captions [Line Items]
Net premiums written	$ 7,977	$ 7,313
Net premiums earned	7,794	7,137
Net investment income	861	836
Equity In Earnings Of Subsidiaries	0	0
Net Realized Gains Losses	(958)	(97)
Losses and loss expenses	4,485	4,098
Policy benefits	129	196
Policy acquisition costs and administrative expenses	2,356	2,174
Interest (income) expense	132	140
Other (income) expense	55	(39)
Amortization of purchased intangibles	73	76
Chubb integration expenses	0	3
Income tax expense	215	188
Net income	252	1,040
Comprehensive income (loss)	(2,460)	2,718
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)	1
Equity In Earnings Of Subsidiaries	256	990
Net Realized Gains Losses	(21)	1
Losses and loss expenses	0	0
Policy benefits	0	0
Policy acquisition costs and administrative expenses	24	20
Interest (income) expense	(34)	(66)
Other (income) expense	(9)	(6)
Amortization of purchased intangibles	0	0
Chubb integration expenses		0
Income tax expense	0	4
Net income	252	1,040
Comprehensive income (loss)	(2,460)	2,718
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	593	759
Net Realized Gains Losses	113	(13)
Losses and loss expenses	0	0
Policy benefits	0	0
Policy acquisition costs and administrative expenses	(38)	(15)
Interest (income) expense	148	185
Other (income) expense	8	3
Amortization of purchased intangibles	0	0
Chubb integration expenses		2
Income tax expense	7	(42)
Net income	585	609
Comprehensive income (loss)	(1,200)	1,941
Other Chubb Limited Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net premiums written	7,977	7,313
Net premiums earned	7,794	7,137
Net investment income	859	839
Equity In Earnings Of Subsidiaries	0	0
Net Realized Gains Losses	(1,050)	(85)
Losses and loss expenses	4,485	4,098
Policy benefits	129	196
Policy acquisition costs and administrative expenses	2,370	2,169
Interest (income) expense	18	21
Other (income) expense	56	(36)
Amortization of purchased intangibles	73	76
Chubb integration expenses		1
Income tax expense	208	226
Net income	264	1,140
Comprehensive income (loss)	(2,418)	2,788
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	(849)	(1,749)
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
Income tax expense	0	0
Net income	(849)	(1,749)
Comprehensive income (loss)	$ 3,618	$ (4,729)