| Document and Entity Information | Aug. 02, 2021 |
| Entity Listings [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 2, 2021 |
| Entity Registrant Name | Argo Group International Holdings, Ltd. |
| Entity Incorporation, State or Country Code | D0 |
| Entity File Number | 001-15259 |
| Entity Tax Identification Number | 98-0214719 |
| Entity Address, Address Line One | 90 Pitts Bay Road |
| Entity Address, City or Town | Pembroke |
| Entity Address, Country | BM |
| Entity Address, Postal Zip Code | HM 08 |
| City Area Code | 441 |
| Local Phone Number | 296-5858 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001091748 |
| Common Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Common Stock, par value of $1.00 per share |
| Trading Symbol | ARGO |
| Security Exchange Name | NYSE |
| Guarantee of Argo Group U.S., Inc. 6.500% Senior Notes due 2042 [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Guarantee of Argo Group U.S., Inc. 6.500% Senior Notes due 2042 |
| Trading Symbol | ARGD |
| Security Exchange Name | NYSE |
| Series A Preferred Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Depositary Shares, Each Representing a 1/1,000th Interest in a 7.00% Resettable Fixed Rate Preference Share, Series A, Par Value $1.00 Per Share |
| Trading Symbol | ARGOPrA |
| Security Exchange Name | NYSE |
