Realized Gains and Losses, Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 1,960	$ 4,339	$ 3,557	$ 9,935
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains	1,296	1,231	3,844	2,405
Losses	(738)	(1,518)	(1,865)	(2,090)
Net realized gains (losses)	558	(287)	1,979	315
Short-term investments
Gain (Loss) on Investments [Line Items]
Gains	407	112	675	26
Losses	(60)	(11)	(143)	(79)
Net realized gains (losses)	347	101	532	(53)
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains	1,071	4,753	1,680	11,078
Losses	(16)	(228)	(634)	(1,405)
Net realized gains (losses)	$ 1,055	$ 4,525	$ 1,046	$ 9,673