Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value
Due in one year or less	$ 133,644
Due after one year through five years	778,875
Due after five years through ten years	295,742
Due after ten years	450,987
Mortgage-backed and asset-backed securities	976,634
Total	2,635,882	$ 2,414,210
Amortized Cost
Due in one year or less	134,931
Due after one year through five years	778,511
Due after five years through ten years	291,811
Due after ten years	444,768
Mortgage-backed and asset-backed securities	978,204
Total	$ 2,628,225	$ 2,400,245