Document and Entity Information Document - shares shares in Millions	3 Months Ended
	Mar. 31, 2017	Apr. 26, 2017
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, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		102.3
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes