Document and Entity Information $ in Billions	12 Months Ended
	Dec. 31, 2020 SFr / shares	Feb. 11, 2021 shares	Jun. 30, 2020 USD ($)	Dec. 31, 2019 SFr / shares
Document Annual Report	true
Document Transition Report	false
Entity Address, Address Line One	Baerengasse 32
Entity Address, City or Town	Zurich
ICFR Auditor Attestation Flag	true
Common Shares, par value | SFr / shares	SFr 24.15			SFr 24.15
Entity Common Stock, Shares Outstanding | shares		450,224,906
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Entity File Number	1-11778
Entity Registrant Name	Chubb Ltd
Entity Incorporation, State or Country Code	V8
Entity Tax Identification Number	98-0091805
Entity Address, Country	CH
Entity Address, Postal Zip Code	8001
Country Region	41
City Area Code	(0)43
Local Phone Number	456 76 00
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000896159
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float | $			$ 57
Common Class A [Member]
Title of 12(b) Security	Common Shares, par value CHF 24.15 per share
Trading Symbol	CB
Security Exchange Name	NYSE
INA Senior Notes Due December 2024 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 0.30% Senior Notes due 2024
Trading Symbol	CB/24A
Security Exchange Name	NYSE
INA Senior Notes Due June 2027 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 0.875% Senior Notes due 2027
Trading Symbol	CB/27
Security Exchange Name	NYSE
INA Senior Notes Due March 2028 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 1.55% Senior Notes due 2028
Trading Symbol	CB/28
Security Exchange Name	NYSE
INA Senior Notes Due December 2029 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 0.875% Senior Notes due 2029
Trading Symbol	CB/29A
Security Exchange Name	NYSE
INA Senior Notes Due June 2031 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 1.40% Senior Notes due 2031
Trading Symbol	CB/31
Security Exchange Name	NYSE
INA Senior Notes Due March 2038 [Member]
Title of 12(b) Security	Guarantee of Chubb INA Holdings Inc. 2.50% Senior Notes due 2038
Trading Symbol	CB/38A
Security Exchange Name	NYSE