Investments - Summary of Gross Investment Gains and Losses before Applicable Income Taxes (Detail) - USD ($) |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2019 |
Sep. 30, 2018 |
|
| Gain (Loss) on Securities [Line Items] | ||||
| Gross investment gains | $ 828,000 | $ 2,981,000 | $ 21,434,000 | $ 6,262,000 |
| Gross investment losses | 1,197,000 | (483,000) | 2,140,000 | 2,200,000 |
| Net investment (losses) gains | (369,041) | 3,463,504 | 19,294,229 | 4,062,475 |
| Fixed Maturities [Member] | ||||
| Gain (Loss) on Securities [Line Items] | ||||
| Gross investment gains | 107,000 | 5,000 | 479,000 | 16,000 |
| Gross investment losses | 4,000 | 25,000 | 324,000 | 70,000 |
| Investments In Affiliates [Member] | ||||
| Gain (Loss) on Securities [Line Items] | ||||
| Gross investment gains | 0 | 12,662,000 | ||
| Equity Securities [Member] | ||||
| Gain (Loss) on Securities [Line Items] | ||||
| Gross investment gains | 721,000 | 2,976,000 | 8,293,000 | 6,246,000 |
| Gross investment losses | $ 1,193,000 | $ (508,000) | $ 1,816,000 | $ 2,130,000 |