REVENUE RECOGNITION (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 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%	96.00%
Net accounts receivable	96.00%		96.00%		97.00%
DIS business | Healthcare Insurers
Segment Reporting Information [Line Items]
Percentage of net revenues	41.00%	35.00%	41.00%	35.00%
Net accounts receivable	31.00%		31.00%		34.00%
DIS business | Healthcare Insurers | Fee-for-service
Segment Reporting Information [Line Items]
Percentage of net revenues	38.00%	32.00%	38.00%	32.00%
DIS business | Healthcare Insurers | Capitated
Segment Reporting Information [Line Items]
Percentage of net revenues	3.00%	3.00%	3.00%	3.00%
DIS business | Government Payers
Segment Reporting Information [Line Items]
Percentage of net revenues	10.00%	12.00%	10.00%	13.00%
Net accounts receivable	6.00%		6.00%		6.00%
DIS business | Client Payers
Segment Reporting Information [Line Items]
Percentage of net revenues	34.00%	39.00%	34.00%	36.00%
Net accounts receivable	42.00%		42.00%		46.00%
DIS business | Patients
Segment Reporting Information [Line Items]
Percentage of net revenues	12.00%	11.00%	12.00%	12.00%
Net accounts receivable	17.00%		17.00%		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%	4.00%
Net accounts receivable	4.00%		4.00%		3.00%