Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Fair Value
Due in one year or less	$ 86,286
Due after one year through five years	516,118
Due after five years through ten years	353,019
Due after ten years	205,612
Mortgage- and asset-backed securities	666,938
Total	1,827,973	1,882,245
Amortized Cost
Due in one year or less	85,378
Due after one year through five years	506,889
Due after five years through ten years	335,229
Due after ten years	195,161
Mortgage- and asset-backed securities	645,771
Total	$ 1,768,428	$ 1,855,598