Schedule of Amortized Cost and Estimated Fair Value of Fixed-Maturity Securities by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Maturity in:
Amortized Cost, 2012	$ 35,037
Amortized Cost, 2013-2016	140,503
Amortized Cost, 2017-2021	37,998
Amortized Cost, Thereafter	50,736
Mortgage-backed securities, Amortized Cost	11,571
Total fixed-maturity securities, Amortized Cost	275,845	298,978
Estimated Fair Value, 2012	34,958
Estimated Fair Value, 2013-2016	144,336
Estimated Fair Value, 2017-2021	38,970
Estimated Fair Value, Thereafter	51,469
Mortgage-backed securities, Estimated Fair Value	11,561
Total fixed-maturity securities, Estimated Fair Value	$ 281,294	$ 304,045