Investments - Summary of Gross Realized Gains and Losses from Investments before Applicable Income Taxes (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Gain (Loss) on Investments [Line Items]
Gross realized gains	$ 731,000	$ 390,000	$ 1,896,000	$ 1,670,000
Gross realized losses	16,000		710,000	233,000
Net realized gains	715,177	390,461	1,186,118	1,436,982
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Gross realized gains	675,000	144,000	1,840,000	967,000
Gross realized losses	3,000		258,000	78,000
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross realized gains	56,000	$ 246,000	56,000	703,000
Gross realized losses	$ 13,000		$ 452,000	$ 155,000