BUSINESS SEGMENT INFORMATION Business Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	100.00%	100.00%
Revenues	$ 3,176.6	$ 3,037.8
Operating Income (Loss)	321.3	329.8
Amortization of Intangible Assets	(60.1)	(53.4)
Net Restructuring Charges	(5.0)	(7.5)
Goodwill and Intangible Asset Impairment	(2.5)	(2.2)
Operating Segments
Segment Reporting Information [Line Items]
Operating Income (Loss)	517.8	515.1
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	14.0	6.3
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	$ (128.9)	$ (122.2)
LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	78.00%	78.00%
Diagnostics
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	78.00%
Diagnostics | Operating Segments
Segment Reporting Information [Line Items]
Revenues	$ 2,479.7	$ 2,382.8
Operating Income (Loss)	$ 417.9	441.5
Drug Development
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	22.00%
Drug Development | Operating Segments
Segment Reporting Information [Line Items]
Revenues	$ 710.9	661.3
Operating Income (Loss)	$ 99.9	$ 73.6