Revenue Recognition and Contractual Adjustments - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 67,746	$ 62,264	$ 131,169	$ 119,693
Clinical Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	59,540	55,547	116,511	108,455
Clinical Services | Client direct billing
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	40,847	36,796	79,561	70,427
Clinical Services | Commercial Insurance
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	8,981	10,124	18,922	21,560
Clinical Services | Medicare and Medicaid
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	9,024	8,403	17,201	16,221
Clinical Services | Self-Pay
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	688	224	827	247
Pharma Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 8,206	$ 6,717	$ 14,658	$ 11,238