Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value
Due in one year or less	$ 128,718
Due after one year through five years	805,858
Due after five years through ten years	301,025
Due after ten years	408,367
Mortgage-backed and asset-backed securities	833,752
Total	2,477,720	$ 2,414,210
Amortized Cost
Due in one year or less	130,610
Due after one year through five years	795,317
Due after five years through ten years	292,205
Due after ten years	391,465
Mortgage-backed and asset-backed securities	823,240
Total	$ 2,432,837	$ 2,400,245