Investments - Schedule of Available-for-Sale Investment Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized Cost
Due in less than 1 year	$ 57,292	$ 45,391
Due in 1-5 years	15,390	13,204
Total	72,682	58,595
Fair Value
Due in less than 1 year	57,246	45,344
Due in 1-5 years	15,363	13,175
Total	$ 72,609	$ 58,519