Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value
Due in one year or less	$ 57,455
Due after one year through five years	768,839
Due after five years through ten years	376,070
Due after ten years	371,003
Mortgage- and asset-backed securities	736,828
Total	2,310,195	2,047,873
Amortized Cost
Due in one year or less	57,822
Due after one year through five years	761,771
Due after five years through ten years	370,373
Due after ten years	362,084
Mortgage- and asset-backed securities	725,334
Total	$ 2,277,384	$ 2,036,999