Segment Information - Summary of Financial Data by Segment (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Premiums earned:
Premiums earned	$ 184,925,733	$ 189,821,058	$ 556,552,279	$ 566,657,613
Net investment income	7,403,251	7,389,749	21,951,679	21,727,904
Investment gains (losses)	3,268,459	(369,041)	(940,488)	19,294,229
Equity in earnings of DFSC				295,000
Other	915,000	1,168,000	2,759,000	3,538,000
Total revenues	196,512,266	198,009,900	580,323,244	611,512,728
Underwriting income (loss):
SAP underwriting income (loss)	4,724,000	(791,000)	21,731,000	(5,131,000)
GAAP adjustments	(1,576,000)	(399,000)	1,186,000	1,431,000
GAAP underwriting income (loss)	3,148,000	(1,190,000)	22,917,000	(3,700,000)
Net investment income	7,403,251	7,389,749	21,951,679	21,727,904
Investment gains (losses)	3,268,459	(369,041)	(940,488)	19,294,229
Equity in earnings of DFSC				295,000
Other	513,000	474,000	894,000	1,070,000
Income before income tax expense	14,331,584	6,304,884	44,822,804	38,687,439
Commercial Lines [Member]
Premiums earned:
Premiums earned	103,436,000	98,324,000	307,080,000	284,593,000
Underwriting income (loss):
SAP underwriting income (loss)	(1,703,000)	2,521,000	2,203,000	4,946,000
Personal Lines [Member]
Premiums earned:
Premiums earned	81,490,000	91,497,000	249,472,000	282,065,000
Underwriting income (loss):
SAP underwriting income (loss)	$ 6,427,000	$ (3,312,000)	$ 19,528,000	$ (10,077,000)