Investments - Summary of Gross Investment Gains and Losses before Applicable Income Taxes (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Gain (Loss) on Securities [Line Items]
Gross investment gains	$ 4,241,000	$ 6,703,000	$ 7,252,000	$ 4,007,000
Gross investment losses	0	217,000	542,000	8,216,000
Net investment gains (losses)	4,241,031	6,485,896	6,710,085	(4,208,947)
Fixed Maturities [Member]
Gain (Loss) on Securities [Line Items]
Gross investment gains	479,000	229,000	524,000	652,000
Gross investment losses	0	217,000	74,000	218,000
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Gross investment gains	3,762,000	6,474,000	6,728,000	3,355,000
Gross investment losses	$ 0	$ 0	$ 468,000	$ 7,998,000