GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 5,848,100,000		$ 5,848,100,000			$ 5,885,600,000
Goodwill	7,422,700,000		7,422,700,000			7,865,000,000.0
Amortization of intangibles and other assets	60,100,000	$ 60,200,000	122,400,000	$ 117,300,000
Amortization of intangible assets	60,100,000	$ 60,200,000	122,400,000	$ 117,300,000
Finite-Lived Intangible Assets, Future Amortization Expense
Estimated amortization expense, 2012	118,200,000		118,200,000
Estimated amortization expense, 2013	235,600,000		235,600,000
Estimated amortization expense, 2014	229,600,000		229,600,000
Estimated amortization expense, 2015	224,200,000		224,200,000
Estimated amortization expense, 2016	219,200,000		219,200,000
Estimated amortization expense, Thereafter	2,311,100,000		2,311,100,000
LabCorp Diagnostics [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	3,732,300,000		3,732,300,000			3,721,500,000
Value of Goodwill Impairment Following a Percentage Change in the Discount Rate Used to Calculate Goodwill for Reporting Unit					$ 40,000,000.0
Covance Drug Development [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 3,690,400,000		$ 3,690,400,000			$ 4,143,500,000