REVENUE (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	100.00%	100.00%	100.00%
Revenues	$ 12,161,600,000	$ 11,863,900,000	$ 13,136,100,000
Percent of Domestic Revenue	83.70%	83.70%	83.60%
Contract with Customer, Asset, before Allowance for Credit Loss	$ 192,900,000	$ 222,300,000
Allowance for Credit Loss, Receivable, Other, Current	(7,500,000)	(10,600,000)
Contract with Customer, Asset, after Allowance for Credit Loss, Current	185,400,000	211,800,000
Contract with Customer, Liability	421,700,000	310,600,000
Deferred Revenue, Revenue Recognized	78,900,000	99,700,000	$ 110,700,000
Accounts Receivable, Allowance for Credit Loss	32,700,000	30,800,000	9,800,000
Unbilled Services, Allowance for Credit Loss	7,500,000	10,500,000	13,900,000
Note Receivable, Allowance for Credit Loss	700,000	700,000	700,000
Allowance for Credit Loss	40,900,000	42,000,000.0	24,400,000
Accounts Receivable, Credit Loss Expense (Reversal)	6,300,000	11,700,000
Unbilled Services, Credit Loss Expense (Reversal)	0	0
Note Receivable, Credit Loss Expense (Reversal)	0	0
Credit Loss Expense (Reversal)	6,300,000	11,700,000
Allowance for Credit Loss, Write Off	$ (7,400,000)	(5,900,000)
Sales Commission Amortization Period Maximum	5 years
Sales Commission Amortization Period Minimum	1 year
Geographic Distribution, Domestic [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 10,177,700,000	$ 9,930,300,000	$ 10,981,200,000
Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	8.00%	8.00%	8.00%
Europe [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	9.00%	9.00%	9.00%
North America
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	87.00%	87.00%	88.00%
Other countries [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	4.00%	3.00%
Covance Drug Development [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed		23.00%
Covance Drug Development [Member] | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	23.00%	23.00%	22.00%
Covance Drug Development [Member] | Europe [Member] | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	9.00%	9.00%	9.00%
Covance Drug Development [Member] | North America | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	10.00%	10.00%	10.00%
Covance Drug Development [Member] | Other countries [Member] | Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	4.00%	3.00%
LabCorp Diagnostics [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	77.00%	77.00%	78.00%
LabCorp Diagnostics [Member] | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	36.00%	39.00%	42.00%
LabCorp Diagnostics [Member] | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	9.00%	8.00%	7.00%
LabCorp Diagnostics [Member] | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	24.00%	22.00%	21.00%
LabCorp Diagnostics [Member] | Europe [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Europe [Member] | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | North America
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	77.00%	77.00%	78.00%
LabCorp Diagnostics [Member] | North America | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	36.00%	39.00%	42.00%
LabCorp Diagnostics [Member] | North America | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	8.00%	8.00%	8.00%
LabCorp Diagnostics [Member] | North America | Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	9.00%	8.00%	7.00%
LabCorp Diagnostics [Member] | North America | Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	24.00%	22.00%	21.00%
LabCorp Diagnostics [Member] | Other countries [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Other countries [Member] | Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] | Other countries [Member] | Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%
Maximum [Member]
Capitalized Contract Cost, Amortization Period	5 years
Capitalized Contract Cost, Amortization Period	5 years
Minimum [Member]
Capitalized Contract Cost, Amortization Period	2 years
Capitalized Contract Cost, Amortization Period	2 years
Accounts Receivable [Member]
Allowance for Credit Loss, Write Off	$ (4,400,000)	$ (9,300,000)
Unbilled Contracts Receivable
Allowance for Credit Loss, Write Off	3,000,000.0	(3,400,000)
Notes Receivable
Allowance for Credit Loss, Write Off	$ 0	$ 0