BASIS OF FINANCIAL STATEMENT PRESENTATION (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Asset Impairment Charges	$ 2.5	$ 2.2
Revenues	3,176.6	$ 3,037.8
Contract with Customer, Liability	$ 377.5		$ 421.7
Percent of Revenue Contributed	100.00%	100.00%
Ownership percentage below which investments are generally accounted for on the cost method (in thousandths)	20.00%
Provision for income taxes	$ 69.1	$ 63.9
Net Income (Loss) Attributable to Parent	228.0	212.9
Stockholders' Equity Attributable to Parent	7,959.6	10,341.5	7,875.0	$ 10,096.6
Deferred Revenue, Revenue Recognized	51.0	$ 52.6
Cash and cash equivalents	$ 99.3		$ 536.8
LabCorp Diagnostics [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of Revenue Contributed	78.00%	78.00%