Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	$ 290,673	$ 317,064
Equity securities, at fair value (cost $44,045 and $44,046 in 2024 and 2023, respectively)	61,923	57,147
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	290,673	317,064
Total	352,596	374,211
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	13,600	13,671
Total	75,523	70,818
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	277,073	303,393
Total	277,073	303,393
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	115,792	131,895
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]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	115,792	131,895
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	156,751	166,753
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]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	156,751	166,753
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]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	4,530	4,745
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]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	4,530	4,745
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	13,600	13,671
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]
Fixed maturity securities-available-for-sale, at fair value (amortized cost $301,691, allowance for credit losses of $0 in 2024 and amortized cost $326,171, allowance for credit losses of $0 in 2023)	13,600	13,671
Fair Value, Measurements, Recurring [Member] | Common Stock [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities, at fair value (cost $44,045 and $44,046 in 2024 and 2023, respectively)	61,923	57,147
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, at fair value (cost $44,045 and $44,046 in 2024 and 2023, respectively)	$ 61,923	$ 57,147