BUSINESS SEGMENT INFORMATION Business Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	100.00%	100.00%	100.00%	100.00%
Revenues	$ 3,056.8	$ 2,866.8	$ 9,128.3	$ 8,934.2
Operating Income (Loss)	252.3	374.0	848.4	1,408.0
Amortization of Intangible Assets	(55.7)	(49.0)	(160.6)	(149.0)
Net Restructuring Charges	(7.5)	(10.0)	(30.8)	(45.0)
Goodwill and Intangible Asset Impairment	(10.2)	0.0	(15.2)	(1.2)
Operating Segments
Segment Reporting Information [Line Items]
Operating Income (Loss)	495.3	544.8	1,524.7	1,932.4
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	7.0	7.2	19.4	31.4
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	$ (169.6)	$ (111.8)	$ (469.7)	$ (329.2)
LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	77.00%	77.00%	77.00%	77.00%
Diagnostics
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	77.00%
Diagnostics | Operating Segments
Segment Reporting Information [Line Items]
Revenues	$ 2,344.7	$ 2,207.6	$ 7,068.3	$ 6,917.1
Operating Income (Loss)	$ 386.3	439.8	1,237.5	1,638.5
Drug Development
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	23.00%
Drug Development | Operating Segments
Segment Reporting Information [Line Items]
Revenues	$ 719.1	666.4	2,079.4	2,048.5
Operating Income (Loss)	$ 109.0	$ 105.0	$ 287.2	$ 293.9