Document and Entity Information Document - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	May 01, 2019
Document Information [Line Items]
Entity Registrant Name	LABORATORY CORP OF AMERICA HOLDINGS
Entity Central Index Key	0000920148
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		98.5
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes