REVENUE - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue recognized	$ 408,363	$ 218,805	$ 1,025,052	$ 580,718
Screening
Disaggregation of Revenue [Line Items]
Revenue recognized	214,623	218,805	565,407	580,718
Screening | Medicare Parts B & C
Disaggregation of Revenue [Line Items]
Revenue recognized	98,847	108,617	256,589	295,103
Screening | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized	106,002	99,352	280,451	261,521
Screening | Other
Disaggregation of Revenue [Line Items]
Revenue recognized	9,774	10,836	28,367	24,094
Precision Oncology
Disaggregation of Revenue [Line Items]
Revenue recognized	91,579	0	322,905	0
Precision Oncology | Medicare Parts B & C
Disaggregation of Revenue [Line Items]
Revenue recognized	33,945	0	114,973	0
Precision Oncology | Commercial
Disaggregation of Revenue [Line Items]
Revenue recognized	37,402	0	137,212	0
Precision Oncology | International Sales
Disaggregation of Revenue [Line Items]
Revenue recognized	16,243	0	56,227	0
Precision Oncology | Other
Disaggregation of Revenue [Line Items]
Revenue recognized	3,989	0	14,493	0
COVID-19 Testing
Disaggregation of Revenue [Line Items]
Revenue recognized	$ 102,161	$ 0	$ 136,740	$ 0