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Fair Value Measurements - Fair Value Measurements for Investments in Available-for-Sale Fixed Maturity and Equity Securities (Detail) - USD ($) | Dec. 31, 2019 | Dec. 31, 2018
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | $ 564,951,803 | $ 526,558,304
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 19,364,459 | 44,209,929
Obligations of States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 56,796,288 | 75,215,969
Corporate Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 159,243,309 | 137,833,145
Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 329,547,747 | 269,299,261
Assets and Liabilities on Recurring Basis [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 570,225,313
Assets and Liabilities on Recurring Basis [Member] | Investments Measured at Net Asset Value [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 12,992,174
Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 620,429,359 | 557,233,139
Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 19,364,459 | 44,209,929
Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Obligations of States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 56,796,288 | 75,215,969
Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Corporate Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 159,243,309 | 137,833,145
Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 329,547,747 | 269,299,261
Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 55,477,556 | 30,674,835
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and Liabilities on Recurring Basis [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 28,351,110
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 53,124,368 | 28,351,110
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 53,124,368 | 28,351,110
Significant Other Observable Inputs (Level 2) [Member] | Assets and Liabilities on Recurring Basis [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 528,882,029
Significant Other Observable Inputs (Level 2) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 567,304,991 | 528,882,029
Significant Other Observable Inputs (Level 2) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 19,364,459 | 44,209,929
Significant Other Observable Inputs (Level 2) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Obligations of States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 56,796,288 | 75,215,969
Significant Other Observable Inputs (Level 2) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Corporate Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 159,243,309 | 137,833,145
Significant Other Observable Inputs (Level 2) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Mortgage-Backed Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 329,547,747 | 269,299,261
Significant Other Observable Inputs (Level 2) [Member] | Assets and Liabilities on Recurring Basis [Member] | Total Investments in the Fair Value Hierarchy [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | $ 2,353,188 | $ 2,323,725

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