Investments - Contractual Maturities of Investments (Details) $ in Thousands	Jun. 30, 2018 USD ($)
Amortized Cost
Amortized Cost	$ 18,422
Fair Value
Fair Value	17,608
Unrestricted available-for-sale, Debt securities
Amortized Cost
Due in one year or less	12,654
Due after one year through five years	2,280
Due after five year through ten years	69
Amortized Cost	15,003
Fair Value
Due in one year or less	12,393
Due after one year through five years	1,711
Due after five years through ten years	98
Fair Value	14,202
Restricted
Amortized Cost
Amortized Cost	3,419
Fair Value
Fair Value	$ 3,406