CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]
BALANCE at Dec. 31, 2018	$ 6,971.4	$ 11.7	$ 1,451.1	$ 7,079.8	$ (1,108.1)	$ (463.1)
Net earnings attributable to Laboratory Corporation of America Holdings	185.6	0.0	0.0	185.6	0.0	0.0
Other comprehensive earnings, net of tax	23.6	0.0	0.0	0.0	0.0	23.6
Issuance of common stock under employee stock plans	(24.7)	0.0	(24.7)	0.0	0.0	0.0
Surrender of restricted stock and performance share awards	(19.4)	0.0	0.0	0.0	(19.4)	0.0
Conversion of zero-coupon convertible debt	7.3
Stock compensation	25.5	0.0	25.5	0.0	0.0	0.0
Purchase of common stock	(100.1)	0.1	100.0	0.0	0.0	0.0
BALANCE at Mar. 31, 2019	7,111.3	11.6	1,401.3	7,265.4	(1,127.5)	(439.5)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	(7.0)	0.0	0.0	(7.0)	0.0	0.0
BALANCE at Dec. 31, 2019	7,567.0	9.0	26.8	7,903.6	0.0	(372.4)
Net earnings attributable to Laboratory Corporation of America Holdings	(317.2)	0.0	0.0	(317.2)	0.0	0.0
Other comprehensive earnings, net of tax	(145.5)	0.0	0.0	0.0	0.0	(145.5)
Issuance of common stock under employee stock plans	(26.9)	0.0	(26.9)	0.0	0.0	0.0
Surrender of restricted stock and performance share awards	(22.0)	0.0	(22.0)	0.0	0.0	0.0
Conversion of zero-coupon convertible debt	0.0
Stock compensation	17.9	0.0	17.9	0.0	0.0	0.0
Purchase of common stock	(100.0)	0.0	49.6	50.4	0.0	0.0
BALANCE at Mar. 31, 2020	$ 7,020.1	$ 9.0	$ 0.0	$ 7,529.0	$ 0.0	$ (517.9)