BUSINESS SEGMENT INFORMATION Business Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total net revenues	$ 2,498.4	$ 2,382.0	$ 4,906.5	$ 4,677.2
Intercompany revenue elimination	(0.4)	(0.1)	(0.5)	(0.2)
Reimbursement Revenue	44.5	48.7	83.4	121.5
Revenues	2,542.9	2,430.7	4,989.9	4,798.7
Operating Income (Loss)	336.0	365.5	668.7	665.0
Earnings before income taxes	285.1	311.9	564.8	565.5
Provision for income taxes	285.1	311.9	564.8	565.5
Provision for income taxes	96.2	107.5	183.4	196.7
Net earnings	188.9	204.4	381.4	368.8
Net income attributable to Laboratory Corporation of America Holdings	(0.3)	(0.3)	(0.6)	(0.6)
Income Loss from Continuing Operations Before Income Taxes and Minority Interest	(50.9)	(53.6)	(103.9)	(99.5)
Net Income (Loss) Attributable to Parent	188.6	204.1	380.8	368.2
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating Income (Loss)	$ (34.3)	(38.8)	$ (67.2)	(77.7)
LabCorp Diagnostics [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	72.00%		71.70%
Total net revenues	$ 1,799.1	1,659.7	$ 3,517.0	3,250.3
Operating Income (Loss)	$ 334.5	329.6	644.0	$ 604.3
Covance Drug Development [Member]
Segment Reporting Information [Line Items]
Percent of Revenue Contributed	28.00%			28.30%
Total net revenues	$ 699.7	722.4	1,390.0	$ 1,427.1
Operating Income (Loss)	$ 35.8	$ 74.7	$ 91.9	$ 138.4