Scheduled Maturity Dates For Fixed Maturity Securities By Number Of Years Until Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value
Due in one year or less	$ 56,876
Due after one year through five years	658,027
Due after five years through ten years	379,158
Due after ten years	230,564
Mortgage- and asset-backed securities	699,804
Total	2,024,429	1,888,069
Amortized Cost
Due in one year or less	56,483
Due after one year through five years	641,379
Due after five years through ten years	353,733
Due after ten years	215,275
Mortgage- and asset-backed securities	668,761
Total	$ 1,935,631	$ 1,816,710