Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fair Value
Due in one year or less	$ 101,673
Due after one year through five years	544,156
Due after five years through ten years	342,481
Due after ten years	196,478
Mortgage- and asset-backed (including GNMAs)	662,433
Total	1,847,221	1,882,245
Amortized Cost
Due in one year or less	100,292
Due after one year through five years	528,318
Due after five years through ten years	331,505
Due after ten years	192,625
Mortgage- and asset-backed (including GNMAs)	646,629
Total	$ 1,799,369	$ 1,855,598