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REVENUE Disaggregated Revenue Table (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Accounts Receivable, Allowance for Credit Loss	$ 26.6		$ 26.6		$ 19.0
Unbilled Services, Allowance for Credit Loss	6.3		6.3		2.3
Note Receivable, Allowance for Credit Loss	5.7		5.7		0.0
Allowance for Credit Loss	$ 38.6		38.6		21.3
Current Expected Credit Losses Opening Balance Sheet Impact on Retained Earnings			7.0
Accounts Receivable, Credit Loss Expense (Reversal)			10.0
Unbilled Services, Credit Loss Expense (Reversal)			3.9
Note Receivable, Credit Loss Expense (Reversal)			0.7
Credit Loss Expense (Reversal)			14.6
Allowance for Credit Loss, Write Off			4.3
Sales Commission Amortization Period Minimum	1 year
Deferred Revenue, Revenue Recognized			237.2	$ 232.8
Contract with Customer, Asset, before Allowance for Credit Loss	$ 609.8		609.8		483.7
Revenue, Remaining Performance Obligation, Amount	$ 4,795.0		$ 4,795.0
Percent of remaining performance obligations recognized as revenue in next year	32.00%		32.00%
Long Term Contracts Duration Minimum	1 year
Long Term Contracts Duration Maximum	8 years
Contract with Customer, Performance Obligation Satisfied in Previous Period			$ 44.8	67.7
Contract with Customer, Liability	$ 492.9		492.9		449.2
Capitalized Contract Cost, Amortization	2.3	$ 2.3	7.6	6.1
Accrued Sales Commission	32.8		32.8		28.6
Capitalized Contract Cost, Net	12.9		12.9		14.9
Amount of Deferred Costs Related to Long-term Contracts	45.7		45.7		43.5
Amortization of Deferred Sales Commissions	6.0	$ 5.8	16.8	$ 15.3
Unbilled Contracts Receivable	$ 603.5		$ 603.5		481.4
Percent of Revenue Contributed	100.00%	100.00%	100.00%	100.00%
Sales Commission Amortization Period Maximum	5 years
Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	7.00%	8.00%	7.00%	8.00%
UNITED STATES
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	82.00%	78.00%	79.00%	78.00%
CANADA
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	2.00%	3.00%	2.00%	3.00%
UNITED KINGDOM
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	5.00%	5.00%	4.00%
SWITZERLAND
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	4.00%	4.00%	5.00%
Europe [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	2.00%	3.00%	3.00%	3.00%
Other countries [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	6.00%	7.00%	7.00%	7.00%
LabCorp Diagnostics [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	68.00%	60.00%	63.00%	61.00%
LabCorp Diagnostics [Member] \| Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	22.00%	17.00%	20.00%	17.00%
LabCorp Diagnostics [Member] \| Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	5.00%	8.00%	6.00%	8.00%
LabCorp Diagnostics [Member] \| Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	34.00%	27.00%	30.00%	28.00%
LabCorp Diagnostics [Member] \| UNITED STATES
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	66.00%	57.00%	61.00%	58.00%
LabCorp Diagnostics [Member] \| UNITED STATES \| Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	21.00%	16.00%	19.00%	16.00%
LabCorp Diagnostics [Member] \| UNITED STATES \| Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	5.00%	8.00%	6.00%	8.00%
LabCorp Diagnostics [Member] \| UNITED STATES \| Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	7.00%	8.00%	7.00%	8.00%
LabCorp Diagnostics [Member] \| UNITED STATES \| Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	33.00%	25.00%	29.00%	26.00%
LabCorp Diagnostics [Member] \| CANADA
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	2.00%	3.00%	2.00%	3.00%
LabCorp Diagnostics [Member] \| CANADA \| Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	1.00%	1.00%	1.00%	1.00%
LabCorp Diagnostics [Member] \| CANADA \| Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| CANADA \| Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| CANADA \| Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	1.00%	2.00%	1.00%	2.00%
LabCorp Diagnostics [Member] \| UNITED KINGDOM
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| UNITED KINGDOM \| Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| UNITED KINGDOM \| Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| UNITED KINGDOM \| Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| UNITED KINGDOM \| Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| SWITZERLAND
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| SWITZERLAND \| Client [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| SWITZERLAND \| Self-Pay [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| SWITZERLAND \| Medicare and Medicaid [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| SWITZERLAND \| Third party [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
LabCorp Diagnostics [Member] \| Europe [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	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%	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%	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%	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%	0.00%
LabCorp Diagnostics [Member] \| Other countries [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	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%	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%	0.00%
Covance Drug Development [Member]
Disaggregation of Revenue [Line Items]
Unbilled Contracts Receivable	$ 834.0		$ 834.0		$ 771.1
Percent of Revenue Contributed	32.00%		37.00%
Covance Drug Development [Member] \| Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	32.00%	40.00%	37.00%	39.00%
Covance Drug Development [Member] \| UNITED STATES \| Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	16.00%	21.00%	18.00%	20.00%
Covance Drug Development [Member] \| CANADA \| Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	0.00%	0.00%	0.00%	0.00%
Covance Drug Development [Member] \| UNITED KINGDOM \| Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	5.00%	5.00%	4.00%
Covance Drug Development [Member] \| SWITZERLAND \| Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	4.00%	4.00%	4.00%	5.00%
Covance Drug Development [Member] \| Europe [Member] \| Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	2.00%	3.00%	3.00%	3.00%
Covance Drug Development [Member] \| Other countries [Member] \| Biopharmaceutical and medical device companies [Member]
Disaggregation of Revenue [Line Items]
Percent of Revenue Contributed	6.00%	7.00%	7.00%	7.00%
Minimum [Member]
Disaggregation of Revenue [Line Items]
Capitalized Contract Cost, Amortization Period	2 years		2 years
Maximum [Member]
Disaggregation of Revenue [Line Items]
Capitalized Contract Cost, Amortization Period	5 years		5 years
Notes Receivable [Member]
Disaggregation of Revenue [Line Items]
Current Expected Credit Losses Opening Balance Sheet Impact on Retained Earnings			$ 5.0
Allowance for Credit Loss, Write Off			0.0
Unbilled Contracts Receivable [Member]
Disaggregation of Revenue [Line Items]
Current Expected Credit Losses Opening Balance Sheet Impact on Retained Earnings			0.2
Allowance for Credit Loss, Write Off			0.1
Accounts Receivable [Member]
Disaggregation of Revenue [Line Items]
Current Expected Credit Losses Opening Balance Sheet Impact on Retained Earnings			1.8
Allowance for Credit Loss, Write Off			$ 4.2