REVENUE - Net Revenue Earned by Category of Payer (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]
Net revenue	$ 781,609	$ 615,880	$ 2,227,897	$ 1,589,638
Commercial payers
Disaggregation of Revenue [Line Items]
Net revenue	644,385	525,927	1,893,105	1,373,481
Government payers
Disaggregation of Revenue [Line Items]
Net revenue	127,435	80,280	308,830	194,875
Patients
Disaggregation of Revenue [Line Items]
Net revenue	$ 9,789	$ 9,673	$ 25,962	$ 21,282