Balance Sheet Components - Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued variable compensation	$ 19,277	$ 22,258
Deferred revenues	7,313	8,111
Current operating lease liabilities	8,379	0
Estimated fair value of contingent consideration liability	8,780	7,156
Other current liabilities	6,659	6,021
Payroll related costs	3,429	3,064
Accrued medical claims expense	1,996	1,431
Professional fees	1,667	1,782
Accrued subcontractor fees	608	563
Total	$ 58,108	$ 50,386