| Document and Entity Information | Feb. 08, 2021 |
| Document And Entity Information [Line Items] | |
| Amendment Flag | true |
| Entity Central Index Key | 0001091748 |
| Document Type | 8-K/A |
| Document Period End Date | Feb. 8, 2021 |
| Entity Registrant Name | Argo Group International Holdings, Ltd. |
| Entity Incorporation State 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, Address Line Two | P.O. Box HM 1282 |
| Entity Address, Address Line Three | Hamilton HM FX |
| Entity Address, City or Town | Pembroke |
| Entity Address, Postal Zip Code | HM 08 |
| Entity Address, Country | BM |
| 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 |
| Amendment Description | In a Current Report on Form 8-K filed on February 8, 2021 (the “Original 8-K”) Argo Group International Holdings, Ltd. (the “Company”) announced the appointment of Scott Kirk as Chief Financial Officer, effective March 1, 2021. As previously announced, Mr. Kirk will succeed Jay Bullock as the Company’s Principal Financial Officer and Principal Accounting Officer, effective at the time of his appointment as Chief Financial Officer. This Form 8-K/A amends the Original 8-K to revise the effective date of Mr. Kirk’s appointment due to an unforeseen delay in the Company’s filing of its annual report on Form 10-K for the fiscal year ended December 31, 2020 (the “2020 10-K”). As a result, Mr. Kirk will become the Chief Financial Officer on the first business day after the Company files the 2020 10-K with the Securities and Exchange Commission. Mr. Bullock will remain the Chief Financial Officer of the Company until such date. |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, par value of $1.00 per share |
| Trading Symbol | ARGO |
| Security Exchange Name | NYSE |
| Guarantee Of Argo Group US Inc 6500 Senior Notes Due 2042 [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Guarantee of Argo Group U.S., Inc. 6.500% Senior Notes due 2042 |
| Trading Symbol | ARGD |
| Security Exchange Name | NYSE |
| Depositary Shares Each Representing A 11000th Interest In A 7.00 Resettable Fixed Rate Preference Share Series A Par Value 1.00 Per Share [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 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 |
