REVENUE - Net Revenue Earned by Category of Payer (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Net revenue	$ 759,237	$ 705,440
Commercial payers
Disaggregation of Revenue [Line Items]
Net revenue	611,434	605,994
Government payers
Disaggregation of Revenue [Line Items]
Net revenue	134,914	86,271
Patients
Disaggregation of Revenue [Line Items]
Net revenue	$ 12,889	$ 13,175