REVENUE RECOGNITION (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%	100.00%	100.00%
Net accounts receivable	100.00%		100.00%		100.00%
DIS business
Segment Reporting Information [Line Items]
Percentage of net revenues	97.00%	97.00%	97.00%	97.00%
Net accounts receivable	97.00%		97.00%		97.00%
DIS business | Healthcare Insurers
Segment Reporting Information [Line Items]
Percentage of net revenues	43.00%	35.00%	42.00%	36.00%
Net accounts receivable	35.00%		35.00%		34.00%
DIS business | Healthcare Insurers | Fee-for-service
Segment Reporting Information [Line Items]
Percentage of net revenues	41.00%	33.00%	39.00%	33.00%
DIS business | Healthcare Insurers | Capitated
Segment Reporting Information [Line Items]
Percentage of net revenues	2.00%	2.00%	3.00%	3.00%
DIS business | Government Payers
Segment Reporting Information [Line Items]
Percentage of net revenues	10.00%	10.00%	10.00%	12.00%
Net accounts receivable	6.00%		6.00%		6.00%
DIS business | Client Payers
Segment Reporting Information [Line Items]
Percentage of net revenues	31.00%	40.00%	33.00%	37.00%
Net accounts receivable	36.00%		36.00%		46.00%
DIS business | Patients
Segment Reporting Information [Line Items]
Percentage of net revenues	13.00%	12.00%	12.00%	12.00%
Net accounts receivable	20.00%		20.00%		11.00%
DIS business | Minimum
Segment Reporting Information [Line Items]
Percentage of net revenues	95.00%	95.00%	95.00%	95.00%
All other operating segments | DS Businesses
Segment Reporting Information [Line Items]
Percentage of net revenues	3.00%	3.00%	3.00%	3.00%
Net accounts receivable	3.00%		3.00%		3.00%