Transactions with Affiliates - Schedule of Southern and Le Mars Assumed from Donegal Mutual Pursuant to Quota-Share Reinsurance Agreements (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Ceded Credit Risk [Line Items]
Losses and loss expenses	$ 140,113,591	$ 114,865,113	$ 102,124,332
Liability for losses and loss expenses	441,714,000
Southern and Le Mars [Member]
Ceded Credit Risk [Line Items]
Premiums earned		(271)	(1,512)
Losses and loss expenses	(104,817)	(690,268)	(378,199)
Liability for losses and loss expenses	$ 719,573	$ 827,193	$ 3,222,100