v3.26.1
Summary of Business Segment Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Revenues:          
Gross written premiums $ 117,096 $ 106,801 $ 213,546 $ 205,476  
Net written premiums 113,971 103,914 206,539 199,778  
Net earned premiums 98,689 95,146 197,044 188,462  
Net losses and loss adjustment expenses 53,047 52,948 106,908 119,686  
Net investment income 16,361 14,707 28,579 29,489  
Net realized investment losses 198 127 (2,045) 263  
Total revenues 116,102 110,520 225,279 219,171  
Corporate expenses (6,842) (7,528) (15,880) (17,028)  
Income before income taxes 14,425 13,129 19,940 8,035  
Income tax expense 3,343 2,785 4,612 1,680  
Net income 11,082 10,344 15,328 6,355  
Total assets 1,723,493 1,720,585 1,723,493 1,720,585 $ 1,720,762
Segment assets          
Revenues:          
Gross written premiums 117,096 106,801 213,546 205,476  
Net written premiums 113,971 103,914 206,539 199,778  
Net earned premiums 98,689 95,146 197,044 188,462  
Commission and service fee income 340 [1] 0 [2] 728 [3] 0 [4]  
Policy and installment fee income 514 540 973 957  
Total segment revenues 99,543 95,686 198,745 189,419  
Net losses and loss adjustment expenses 53,047 [5] 52,948 [6] 106,908 [7] 119,686 [8]  
Net commission expenses 24,049 [5] 21,843 [6] 47,387 [7] 44,177 [8]  
Other operating expenses 17,739 [5],[9] 15,072 [6],[10] 35,164 [7],[11] 30,245 [8],[12]  
Income (loss) from segments 4,708 [5] 5,823 [6] 9,286 [7] (4,689) [8]  
Total assets 275,789 254,257 275,789 254,257  
Corporate assets          
Revenues:          
Net investment income 16,361 14,707 28,579 29,489  
Net realized investment losses 198 127 (2,045) 263  
Total assets 1,447,704 1,466,328 1,447,704 1,466,328  
Elimination          
Revenues:          
Gross written premiums 0 0 0 0  
Net written premiums 0 0 0 0  
Net earned premiums 0   0 0  
Commission and service fee income (13,412) [1] (14,851) [2] (25,802) [3] (28,900) [4]  
Policy and installment fee income 0 0   0  
Total segment revenues (13,412) (14,851) (25,802) (28,900)  
Net losses and loss adjustment expenses (328) [5] (332) [6] (769) [7] (665) [8]  
Net commission expenses (10,482) [5] (11,456) [6] (20,006) [7] (22,027) [8]  
Other operating expenses (2,602) [5],[9] (3,063) [6],[10] (5,027) [7],[11] (6,208) [8],[12]  
Income (loss) from segments 0 [5] 0 [6] 0 [7] 0 [8]  
Total assets (15,704) (19,644) (15,704) (19,644)  
Agency and Insurance Services | Segment assets          
Revenues:          
Gross written premiums 0 0 0 0  
Net written premiums 0 0 0 0  
Net earned premiums 0 0 0 0  
Commission and service fee income 13,752 [1] 14,851 [2] 26,530 [3] 28,900 [4]  
Policy and installment fee income 523 499 984 886  
Total segment revenues 14,275 15,350 27,514 29,786  
Net losses and loss adjustment expenses 0 [5] 0 [6] 0 [7] 0 [8]  
Net commission expenses 0 [5] 0 [6] 0 [7] 0 [8]  
Other operating expenses 12,916 [5],[9] 13,042 [6],[10] 26,549 [7],[11] 25,674 [8],[12]  
Income (loss) from segments 1,359 [5] 2,308 [6] 965 [7] 4,112 [8]  
Total assets 46,112 33,730 46,112 33,730  
Belmont Core | Segment assets          
Revenues:          
Gross written premiums 117,257 109,819 213,764 208,208  
Net written premiums 114,134 106,873 206,759 202,507  
Net earned premiums 98,834 97,513 197,205 189,773  
Commission and service fee income 0 [1] 0 [2] 0 [3] 0 [4]  
Policy and installment fee income 0 0 0 0  
Total segment revenues 98,834 97,513 197,205 189,773  
Net losses and loss adjustment expenses 53,480 [5] 56,109 [6] 107,784 [7] 122,561 [8]  
Net commission expenses 34,615 [5] 34,079 [6] 67,310 [7] 66,483 [8]  
Other operating expenses 7,365 [5],[9] 4,591 [6],[10] 13,495 [7],[11] 9,577 [8],[12]  
Income (loss) from segments 3,374 [5] 2,734 [6] 8,616 [7] (8,848) [8]  
Total assets 170,355 154,811 170,355 154,811  
Belmont Non-Core | Segment assets          
Revenues:          
Gross written premiums (161) (3,018) (218) (2,732)  
Net written premiums (163) (2,959) (220) (2,729)  
Net earned premiums (145) (2,367) (161) (1,311)  
Commission and service fee income 0 [1] 0 [2] 0 [3] 0 [4]  
Policy and installment fee income (9) 41 (11) 71  
Total segment revenues (154) (2,326) (172) (1,240)  
Net losses and loss adjustment expenses (105) [5] (2,829) [6] (107) [7] (2,210) [8]  
Net commission expenses (84) [5] (780) [6] 83 [7] (279) [8]  
Other operating expenses 60 [5],[9] 502 [6],[10] 147 [7],[11] 1,202 [8],[12]  
Income (loss) from segments (25) [5] 781 [6] (295) [7] 47 [8]  
Total assets $ 75,026 $ 85,360 $ 75,026 $ 85,360  
[1] Consists of intersegment revenues of $13.4 million, which are eliminated in consolidation, and third party commission and service fee income of $0.3 million in 2026.
[2] Consists of intersegment revenues of $14.9 million, which are eliminated in consolidation.
[3] Consists of intersegment revenues of $25.8 million, which are eliminated in consolidation, and third party commission and service fee income of $0.7 million in 2026.
[4] Consists of intersegment revenues of $28.9 million, which are eliminated in consolidation.
[5] The significant expense categories and amounts align with the segment-level information that is regularly provided to the CODM.
[6] The significant expense categories and amounts align with the segment-level information that is regularly provided to the CODM.
[7] The significant expense categories and amounts align with the segment-level information that is regularly provided to the CODM.
[8] The significant expense categories and amounts align with the segment-level information that is regularly provided to the CODM.
[9] Other operating expenses consist primarily of personnel expenses and general operating expenses related to underwriting and distribution activities.
[10] Other operating expenses consist primarily of personnel expenses and general operating expenses related to underwriting activities.
[11] Other operating expenses consist primarily of personnel expenses and general operating expenses related to underwriting and distribution activities.
[12] Other operating expenses consist primarily of personnel expenses and general operating expenses related to underwriting activities.