Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	$ 419,036	$ 441,146
Equity securities, Fair Value	27,910	27,903
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	419,036	441,146
Total	446,946	469,049
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	33,096	40,126
Total	61,006	68,029
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	385,940	401,020
Total	385,940	401,020
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	237,914	237,775
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	237,914	237,775
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	113,813	133,778
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	113,813	133,778
Fair Value, Measurements, Recurring [Member] | U.S. Agency-Based Mortgage-Backed Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	34,213	29,467
Fair Value, Measurements, Recurring [Member] | U.S. Agency-Based Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	34,213	29,467
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	33,096	40,126
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale—fixed maturity, Fair Value	33,096	40,126
Fair Value, Measurements, Recurring [Member] | Common Stock [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities, Fair Value	27,910	27,903
Fair Value, Measurements, Recurring [Member] | Common Stock [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities, Fair Value	$ 27,910	$ 27,903