Realized Gains And Losses Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 1,842	$ (1,389)
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains	3,142	2,867
Losses	(1,300)	(4,256)
Net realized gains (losses)	$ 1,842	$ (1,389)