Realized Gains and Losses Excluding Net Other-Than-Temporary Impairment Losses Recognized in Earnings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Gain (Loss) on Investments [Line Items]
Net realized gains (losses)	$ 15,768	$ (988)	$ 3,345	$ 4,814	$ 30,254	$ 4,761	$ 4,217	$ 1,842	$ 22,939	$ 41,074	$ 11,996
Fixed maturities
Gain (Loss) on Investments [Line Items]
Gains									8,539	28,789	11,678
Losses									(2,797)	(1,915)	(7,044)
Net realized gains (losses)									5,742	26,874	4,634
Equity Securities
Gain (Loss) on Investments [Line Items]
Gains									17,955	14,673	9,319
Losses									(758)	(473)	(1,957)
Net realized gains (losses)									$ 17,197	$ 14,200	$ 7,362