Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Operations) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Condensed Statement of Income Captions [Line Items]
Net investment income		$ 863	$ 861
Realized Investment Gains (Losses)		887	(958)
Administrative expenses		(744)	(741)
Interest (income) expense		(122)	(132)
Other (income) expense		(490)	55
Income tax expense		(338)	(215)
Net income		2,300	252
Comprehensive income (loss)		389	(2,460)
Chubb Limited (Parent Guarantor)
Condensed Statement of Income Captions [Line Items]
Net investment income	[1]	1	(2)
Realized Investment Gains (Losses)	[1]	13	(21)
Administrative expenses	[1]	22	24
Interest (income) expense	[1]	(34)	(34)
Other (income) expense	[1]	(13)	(9)
Income tax expense	[1]	11	0
Net income	[1],[2]	28	(4)
Comprehensive income (loss)	[1]	28	(4)
Equity In Earnings Of Subsidiaries		2,272	256
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Statement of Income Captions [Line Items]
Net investment income		1	4
Realized Investment Gains (Losses)		67	113
Administrative expenses		(52)	(38)
Interest (income) expense		145	148
Other (income) expense		(5)	8
Income tax expense		(22)	7
Net income	[2]	2	(8)
Comprehensive income (loss)		1	(38)
Equity In Earnings Of Subsidiaries		$ 1,031	$ 593

[1] Excludes investment in subsidiary issuer (presented separately).

[2] Net income of Parent Guarantor excludes equity in earnings from investment in subsidiaries, including Subsidiary Issuer, of $2,272 million and $256 million for the three months ended March 31, 2021 and 2020, respectively. Net income of Subsidiary Issuer excludes equity in earnings from investment in subsidiaries of $1,031 million and $593 million for the three months ended March 31, 2021 and 2020, respectively.