Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Mar. 25, 2025	Jun. 30, 2024
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2024
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-15259
Entity Registrant Name	ARGO GROUP INTERNATIONAL HOLDINGS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	98-0214719
Entity Address, Address Line One	501 7th Avenue 7th Floor
Entity Address, City or Town	New York
Entity Address, Postal Zip Code	10018
Entity Address, State or Province	NY
City Area Code	210
Local Phone Number	321-8400
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 0.0
Entity Common Stock, Shares Outstanding		13
Entity Central Index Key	0001091748
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Amendment Flag	false
Guarantee of Argo Group U.S., Inc. 6.500% Senior Notes due 2042
Document Information [Line Items]
Title of 12(b) Security	6.500% Senior Notes due 2042 issued by Argo Group US, Inc.  and The Guarantee with Respects Thereto
Trading Symbol	ARGD
Security Exchange Name	NYSE
Depositary Shares
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares, Each Representing a 1/1000th Interest in 7.00% Resettable Fixed Rate Preferred Stock, Series A, Par Value $1.00 Per Share
Trading Symbol	ARGO/PA
Security Exchange Name	NYSE