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Company's Invested Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | $ 1,315,399 | $ 1,381,908
Equity securities | 12,408 | 12,284
U.S. Treasuries |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 543,510 | 875,246
Obligations of States and Political Subdivisions |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 16,484 | 16,335
Mortgage Backed Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 208,636 | 58,920
Commercial Mortgage-Backed Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 67,557 | 65,568
Asset-backed Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 141,700 | 135,427
Corporate Bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 245,884 | 156,096
Foreign Corporate Bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 91,628 | 74,316
Fair Value, Measurements, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 1,315,399 | 1,381,908
Equity securities | 12,408 | 12,284
Total invested assets | 1,327,807 | 1,394,192
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 543,510 | 875,246
Equity securities | 0 | 0
Total invested assets | 543,510 | 875,246
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 771,889 | 506,662
Equity securities | 12,408 | 12,284
Total invested assets | 784,297 | 518,946
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Equity securities | 0 | 0
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | U.S. Treasuries |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 543,510 | 875,246
Fair Value, Measurements, Recurring | U.S. Treasuries | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 543,510 | 875,246
Fair Value, Measurements, Recurring | U.S. Treasuries | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | U.S. Treasuries | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Obligations of States and Political Subdivisions |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 16,484 | 16,335
Fair Value, Measurements, Recurring | Obligations of States and Political Subdivisions | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Obligations of States and Political Subdivisions | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 16,484 | 16,335
Fair Value, Measurements, Recurring | Obligations of States and Political Subdivisions | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Mortgage Backed Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 208,636 | 58,920
Fair Value, Measurements, Recurring | Mortgage Backed Securities | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Mortgage Backed Securities | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 208,636 | 58,920
Fair Value, Measurements, Recurring | Mortgage Backed Securities | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Commercial Mortgage-Backed Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 67,557 | 65,568
Fair Value, Measurements, Recurring | Commercial Mortgage-Backed Securities | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Commercial Mortgage-Backed Securities | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 67,557 | 65,568
Fair Value, Measurements, Recurring | Commercial Mortgage-Backed Securities | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Asset-backed Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 141,700 | 135,427
Fair Value, Measurements, Recurring | Asset-backed Securities | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Asset-backed Securities | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 141,700 | 135,427
Fair Value, Measurements, Recurring | Asset-backed Securities | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Corporate Bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 245,884 | 156,096
Fair Value, Measurements, Recurring | Corporate Bonds | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Corporate Bonds | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 245,884 | 156,096
Fair Value, Measurements, Recurring | Corporate Bonds | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Foreign Corporate Bonds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 91,628 | 74,316
Fair Value, Measurements, Recurring | Foreign Corporate Bonds | Fair Value, Inputs, Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 0 | 0
Fair Value, Measurements, Recurring | Foreign Corporate Bonds | Fair Value, Inputs, Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | 91,628 | 74,316
Fair Value, Measurements, Recurring | Foreign Corporate Bonds | Fair Value, Inputs, Level 3 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Total invested assets | $ 0 | $ 0

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