XML 162 R124.htm IDEA: XBRL DOCUMENT v3.22.0.1
Statutory Accounting Principles - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Argo Re      
Statutory Accounting Practices [Line Items]      
Maximum permissible limit for dividend 25.00%    
Reduction in total statutory capital 15.00%    
Maximum permitted amount of dividends $ 356.4    
Cash dividends 85.0 $ 58.8 $ 52.1
Argonaut Insurance Company      
Statutory Accounting Practices [Line Items]      
Maximum permitted amount of dividends 107.1    
Rockwood Casualty Insurance Company      
Statutory Accounting Practices [Line Items]      
Maximum permitted amount of dividends 10.6    
Minimum      
Statutory Accounting Practices [Line Items]      
Minimum statutory capital and surplus balance $ 126.8 $ 201.3