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, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Net revenue	$ 860,272				$ 740,848	$ 1,619,509	$ 1,446,288
Commercial payers
Disaggregation of Revenue [Line Items]
Net revenue	746,647	$ 648,507	$ 690,686	$ 678,706	642,726	1,395,154	1,248,720	$ 1,927,426	$ 2,618,112
Government payers
Disaggregation of Revenue [Line Items]
Net revenue	102,581	$ 97,841	$ 100,431	$ 93,114	95,124	200,422	181,395	$ 274,509	$ 374,940
Patients
Disaggregation of Revenue [Line Items]
Net revenue	$ 11,044				$ 2,998	$ 23,933	$ 16,173