REVENUE - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue recognized	$ 268,868	$ 199,870	$ 616,689	$ 361,913
Screening
Disaggregation of Revenue [Line Items]
Revenue recognized	131,333	199,870	350,784	361,913
Screening | Medicare Parts B & C
Disaggregation of Revenue [Line Items]
Revenue recognized	59,583	103,569	157,742	186,486
Screening | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized	65,080	88,818	174,449	162,169
Screening | Other
Disaggregation of Revenue [Line Items]
Revenue recognized	6,670	7,483	18,593	13,258
Precision Oncology
Disaggregation of Revenue [Line Items]
Revenue recognized	102,956	0	231,326	0
Precision Oncology | Medicare Parts B & C
Disaggregation of Revenue [Line Items]
Revenue recognized	33,994	0	81,028	0
Precision Oncology | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized	45,420	0	99,810	0
Precision Oncology | International Sales
Disaggregation of Revenue [Line Items]
Revenue recognized	19,018	0	39,980	0
Precision Oncology | Other
Disaggregation of Revenue [Line Items]
Revenue recognized	4,524	0	10,508	0
COVID-19 Testing
Disaggregation of Revenue [Line Items]
Revenue recognized	$ 34,579	$ 0	$ 34,579	$ 0