Investments - Summary of Gross Realized Gains and Losses from Investments before Applicable Income Taxes (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Gain (Loss) on Investments [Line Items]
Gross realized gains	$ 390,000	$ 2,034,000	$ 1,670,000	$ 2,000,000
Gross realized losses			233,000	54,000
Net realized gains	390,461	2,034,172	1,436,982	1,945,640
Fixed Maturities [Member]
Gain (Loss) on Investments [Line Items]
Gross realized gains	144,000	1,325,000	967,000	1,348,000
Gross realized losses			78,000	1,000
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Gross realized gains	$ 246,000	$ 709,000	703,000	652,000
Gross realized losses			$ 155,000	$ 53,000