REVENUE - Net Revenue Earned by Category of Payer (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2021	Sep. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Net revenue							$ 3,438,640	$ 3,032,610	$ 2,310,417
Commercial payers
Disaggregation of Revenue [Line Items]
Net revenue	$ 746,647	$ 648,507	$ 690,686	$ 678,706	$ 1,395,154	$ 1,927,426	2,971,900	2,618,112	2,001,105
Government payers
Disaggregation of Revenue [Line Items]
Net revenue	$ 102,581	$ 97,841	$ 100,431	$ 93,114	$ 200,422	$ 274,509	417,088	374,940	285,128
Patients
Disaggregation of Revenue [Line Items]
Net revenue							$ 49,652	$ 39,558	$ 24,184