Revenue Recognition and Contractual Adjustments - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 63,423	$ 57,427
Clinical Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	56,971	52,906
Clinical Services | Client direct billing
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	38,530	33,630
Clinical Services | Commercial Insurance
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	10,326	11,436
Clinical Services | Medicare and Medicaid
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	8,084	7,818
Clinical Services | Self-Pay
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	31	22
Pharma Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenues	$ 6,452	$ 4,521