SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Patient Accounts Receivable Narrative (Details)	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Concentration Risk [Line Items]
Accounts receivable derived from Medicare	69.00%	68.00%
Net service revenue period of care payment rate (days)	30 days
Percentage of patient receivables outstanding	10.00%
Historical collection rate from Medicare	99.00%