QUARTERLY DATA (UNAUDITED) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of unaudited quarterly data
Net sales	$ 1,512.7	$ 1,551.8	$ 1,516.4	$ 1,430.7	$ 1,437.0	$ 1,462.2	$ 1,468.2	$ 1,440.9	$ 6,011.6	$ 5,808.3	$ 5,671.4
Cost of Goods and Services Sold									3,808.5	3,585.1	3,421.7
Gross profit	546.5	571.2	568.6	516.8	526.1	547.6	577.3	572.2	2,203.1	2,223.2	2,249.7
Net earnings attributable to Laboratory Corporation of America Holdings	$ 119.6	$ 137.2	$ 141.3	$ 113.1	$ 126.4	$ 148.3	$ 151.9	$ 147.2	$ 511.2	$ 573.8	$ 583.1
Earnings Per Share
Basic earnings per share (in dollars per share)	$ 1.41	$ 1.62	$ 1.67	$ 1.33	$ 1.46	$ 1.66	$ 1.65	$ 1.58	$ 6.03	$ 6.36	$ 6.09
Diluted earnings per common share (in dollars per share)	$ 1.37	$ 1.59	$ 1.64	$ 1.31	$ 1.43	$ 1.63	$ 1.62	$ 1.56	$ 5.91	$ 6.25	$ 5.99