Investments - Contractual maturity periods (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less	$ 7,010
Due after one year through five years	13,489
Due after five years through ten years	671
Due after ten years	966
Total	22,136	$ 12,432
Estimated Fair Value
Due in one year or less	7,011
Due after one year through five years	13,554
Due after five years through ten years	672
Due after ten years	958
Fixed maturity securities	$ 22,195	$ 12,260