v3.25.1
Cover - shares
 3 Months Ended
Mar. 31, 2025
May 08, 2025
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
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 Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   13
Entity Central Index Key 0001091748  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
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