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Long-Term Debt - Additional Information (Detail) - USD ($)
1 Months Ended 10 Months Ended 12 Months Ended
Dec. 31, 2022
Oct. 31, 2022
Nov. 23, 2021
Aug. 31, 2021
Oct. 31, 2022
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2006
Nov. 09, 2006
Debt Instrument [Line Items]                    
Surplus note $ 5,500,000         $ 5,500,000        
Principal repayments of Surplus Note           1,500,000 $ 1,500,000 $ 1,500,000    
Surplus during the term of surplus note           $ 50,000,000        
Revolving Credit Facility | Prime Rate                    
Debt Instrument [Line Items]                    
Debt instrument, basis spread on variable rate   2.00%                
2021 Revolving Loan | Revolving Credit Facility                    
Debt Instrument [Line Items]                    
Line of credit facility, expiration period       364 days            
Line of credit facility, maximum borrowing capacity   $ 35,000,000     $ 35,000,000          
Borrowings on line of credit facility         0          
2022 Revolving Loan | Revolving Credit Facility                    
Debt Instrument [Line Items]                    
Line of credit facility, expiration period   364 days                
Line of credit facility, maximum borrowing capacity   $ 37,500,000     $ 37,500,000          
Line of credit facility, unused capacity, commitment fee percentage   0.50%                
Borrowings on line of credit facility $ 0                  
Surplus note                    
Debt Instrument [Line Items]                    
Unsecured term loan agreement                   $ 25,000,000
Debt term                 20 years  
Effective interest rate 2.83%         2.83% 1.50% 1.05%    
Principal repayments of Surplus Note           $ 368,000        
Maturity year of debt instrument           through 2026        
Net written premium to surplus ratio           200.00%        
Gross written premium to surplus ratio           600.00%        
Surplus note | Hurricane                    
Debt Instrument [Line Items]                    
Surplus and Reinsurance sufficient to cover in excess of UPCIC probable maximum loss           1-in-100 year        
Unsecured Debt                    
Debt Instrument [Line Items]                    
Repurchased amount     $ 100,000,000              
Unsecured Debt | 5.625% Senior Unsecured Notes Due 2026                    
Debt Instrument [Line Items]                    
Unsecured term loan agreement     $ 100,000,000              
Maturity year of debt instrument     2026              
Stated percentage 5.625%         5.625%        
Unsecured Debt | 5.625% Senior Unsecured Notes Due 2026 | Debt Instrument, Redemption, Period One                    
Debt Instrument [Line Items]                    
Redemption price     102.8125%              
Unsecured Debt | 5.625% Senior Unsecured Notes Due 2026 | Debt Instrument, Redemption, Period Two                    
Debt Instrument [Line Items]                    
Redemption price     101.40625%              
Unsecured Debt | 5.625% Senior Unsecured Notes Due 2026 | Debt Instrument, Redemption, Period Three                    
Debt Instrument [Line Items]                    
Redemption price     100.00%