Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value
Due in one year or less	$ 81,849
Due after one year through five years	810,165
Due after five years through ten years	296,471
Due after ten years	464,767
Mortgage-backed and asset-backed securities	1,007,165
Total	2,660,417	$ 2,414,210
Amortized Cost
Due in one year or less	83,551
Due after one year through five years	799,159
Due after five years through ten years	281,368
Due after ten years	438,852
Mortgage-backed and asset-backed securities	988,120
Total	$ 2,591,050	$ 2,400,245