Realized Gains and Losses Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 6,718	$ (988)	$ 12,024	$ 7,171
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains	3,702	1,099	8,682	6,035
Losses	(1,645)	(2,087)	(3,752)	(2,470)
Net realized gains (losses)	2,057	(988)	4,930	3,565
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains	6,109		9,445	3,733
Losses	(1,448)		(2,351)	(127)
Net realized gains (losses)	$ 4,661		$ 7,094	$ 3,606