Schedule of Sales of Fixed Maturity and Equity Securities Excluding Maturities and Calls (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
Investment Securities [Line Items]        
Proceeds $ 5,378 $ 9,714 $ 13,994 $ 61,255
Gross realized gains 399 292 712 3,944
Gross realized losses $ (44) $ (76) $ (76) $ (1,666)