Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value
Due in one year or less	$ 173,505
Due after one year through five years	732,625
Due after five years through ten years	321,037
Due after ten years	503,965
Mortgage-backed and asset-backed securities	964,145
Total	2,695,277	$ 2,635,882
Amortized Cost
Due in one year or less	174,014
Due after one year through five years	730,523
Due after five years through ten years	315,580
Due after ten years	492,950
Mortgage-backed and asset-backed securities	965,408
Total	$ 2,678,475	$ 2,628,225