Investments (Details 2) $ in Thousands	Sep. 30, 2017 USD ($)
Amortized cost
Due in one year or less	$ 65,085
Due after one year through five years	332,904
Due after five years through ten years	239,042
Due after ten years	103,778
Amortized cost, fixed maturities	740,809
Estimated fair value
Due in one year or less	65,208
Due after one year through five years	337,986
Due after five years through ten years	242,425
Due after ten years	103,647
Estimated fair value, fixed maturities	$ 749,266