Amortized Cost/Cost, Gross Unrealized Gains and Losses, Estimated Fair Values and Impairments Reflected in Other Comprehensive Income of Investments in Fixed Maturity and Equity Available-for-Sale Securities (Parenthetical) (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Unrealized gains	$ 1,837	$ 2,515