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, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 4,761	$ 3,238	$ 10,820	$ 4,856
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains	4,011	3,315	11,868	10,625
Losses	(216)	(77)	(1,746)	(6,610)
Net realized gains (losses)	3,795	3,238	10,122	4,015
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains	966		1,171	841
Losses			(473)
Net realized gains (losses)	$ 966		$ 698	$ 841