Realized Gains and Losses, Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 8,373	$ 12,812	$ 22,939
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains	4,756	8,326	8,539
Losses	(5,926)	(2,610)	(2,797)
Net realized gains (losses)	(1,170)	5,716	5,742
Short-term investments
Gain (Loss) on Investments [Line Items]
Gains	130
Losses	(383)
Net realized gains (losses)	(253)
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains	14,331	9,447	17,955
Losses	(4,535)	(2,351)	(758)
Net realized gains (losses)	$ 9,796	$ 7,096	$ 17,197