Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Inputs, Level 1
Assets:
Short-term investments	$ 21,970	$ 42,942
Total	21,970	42,942
Fair Value, Inputs, Level 3
Liabilities:
Contingent consideration	2,100	2,100
Total	$ 2,100	$ 2,100