Scheduled Maturity Dates for Fixed Maturity Securities by Number of Years Until Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value
Due in one year or less	$ 208,510
Due after one year through five years	719,399
Due after five years through ten years	313,225
Due after ten years	574,582
Mortgage-Backed and Asset-Backed Securities	934,688
Total	2,750,404	$ 2,635,882
Amortized Cost
Due in one year or less	208,573
Due after one year through five years	714,152
Due after five years through ten years	305,230
Due after ten years	555,096
Mortgage-Backed and Asset-Backed Securities	932,859
Total	$ 2,715,910	$ 2,628,225