Investments - Schedule of Available-for-Sale Investment Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Amortized Cost
Due in less than 1 year	$ 47,839	$ 83,030
Due in 1-3 years	2,461	17,359
Total	50,300	100,389
Fair Value
Due in less than 1 year	47,870	82,893
Due in 1-3 years	2,479	17,325
Total	$ 50,349	$ 100,218