Transactions with Affiliates - Schedule of Reinsurance Atlantic States Ceded to Pool (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Ceded Credit Risk [Line Items]
Premiums earned	$ 314,859,014	$ 326,198,234	$ 310,179,267
Prepaid reinsurance premiums	142,475,767	135,379,777
Affiliated Entity [Member] | Atlantic States Ceded [Member]
Ceded Credit Risk [Line Items]
Premiums earned	218,642,984	212,928,238	200,752,599
Losses and loss expenses	173,238,503	159,495,489	140,015,950
Prepaid reinsurance premiums	116,189,929	106,224,424	103,991,861
Liability for losses and loss expenses	$ 183,326,589	$ 158,081,925	$ 136,786,070