Segment Information - Summary of Financial Data by Segment (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Premiums earned:
Premiums earned	$ 187,661,705	$ 177,283,816	$ 555,140,395	$ 521,454,835
Net investment income	6,620,491	5,979,834	19,341,012	17,385,103
Realized investment gains	3,463,504	561,429	4,062,475	4,207,710
Equity in earnings of DFSC	732,768	403,647	2,152,738	1,023,212
Other	1,426,000	1,487,000	4,326,000	4,197,000
Total revenues	199,904,180	185,716,027	585,022,486	548,267,706
Underwriting (loss) income:
SAP underwriting (loss) income	(10,085,000)	79,000	(60,293,000)	(19,146,000)
GAAP adjustments	332,000	644,000	5,106,000	6,423,000
GAAP underwriting (loss) income	(9,753,000)	723,000	(55,187,000)	(12,723,000)
Net investment income	6,620,491	5,979,834	19,341,012	17,385,103
Realized investment gains	3,463,504	561,429	4,062,475	4,207,710
Equity in earnings of DFSC	732,768	403,647	2,152,738	1,023,212
Other	213,000	844,000	1,040,000	1,947,000
(Loss) income before income tax (benefit) expense	1,276,986	8,512,050	(28,591,231)	11,840,410
Commercial Lines [Member]
Premiums earned:
Premiums earned	84,251,000	80,724,000	251,029,000	236,437,000
Underwriting (loss) income:
SAP underwriting (loss) income	2,125,000	8,998,000	(17,935,000)	12,670,000
Personal Lines [Member]
Premiums earned:
Premiums earned	103,410,000	96,560,000	304,111,000	285,018,000
Underwriting (loss) income:
SAP underwriting (loss) income	$ (12,210,000)	$ (8,919,000)	$ (42,358,000)	$ (31,816,000)