Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value
Due in one year or less	$ 82,515
Due after one year through five years	802,221
Due after five years through ten years	307,813
Due after ten years	409,862
Mortgage-backed and asset-backed securities	794,576
Total	2,396,987	$ 2,365,934
Amortized Cost
Due in one year or less	86,268
Due after one year through five years	794,442
Due after five years through ten years	302,656
Due after ten years	400,390
Mortgage-backed and asset-backed securities	783,416
Total	$ 2,367,172	$ 2,323,959