Investments - Summary of Gross Investment Gains and Losses before Applicable Income Taxes (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Gain (Loss) on Securities [Line Items]
Gross investment gains	$ 854,000	$ 19,006,000
Gross investment losses	11,549,000	909,000
Net investment (losses) gains	(10,694,843)	18,097,113
Fixed Maturities [Member]
Gain (Loss) on Securities [Line Items]
Gross investment gains	423,000	358,000
Gross investment losses	1,000	318,000
Investments In Affiliates [Member]
Gain (Loss) on Securities [Line Items]
Gross investment gains		12,662,000
Equity Securities [Member]
Gain (Loss) on Securities [Line Items]
Gross investment gains	431,000	5,986,000
Gross investment losses	$ 11,548,000	$ 591,000