SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($)

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Accounting Policies [Abstract]

Goodwill, Impairment Loss

$ 333,600,000

$ 260,000,000.0

Inventory Valuation Reserves

66,100,000

23,300,000

Accounts receivable balances (gross) from Medicare and Medicaid

$ 86,500,000

85,800,000

Ownership percentage below which investments are generally accounted for on the cost method (in hundredths)

20.00%

Cash, Uninsured Amount

$ 534,700,000

$ 428,100,000

Minimum threshold percentage required to recognize income tax benefit (in hundredths)

50.00%

Percent of gross accounts receivable due from patients

20.40%

15.30%

Inventory, Finished Goods, Gross

$ 89,500,000

$ 57,800,000

Other Inventory, Supplies, Gross

385,100,000

412,800,000

Goodwill and Intangible Asset Impairment

349,000,000.0

261,700,000

$ 0

Goodwill

$ 6,142,500,000

$ 6,123,700,000

$ 5,891,000,000

Earnings Per Share

Earnings per Share

Basic earnings per share is computed by dividing net earnings attributable to Laboratory Corporation of America Holdings by the weighted average number of common shares outstanding. Diluted earnings per share is computed by dividing net earnings including the impact of dilutive adjustments by the weighted average number of common shares outstanding plus potentially dilutive shares, as if they had been issued at the earlier of the date of issuance or the beginning of the period

presented. Potentially dilutive common shares result primarily from the Company’s outstanding stock options, restricted stock awards, performance share awards, and accelerated share repurchases.

The following represents a reconciliation of basic earnings per share to diluted earnings per share: 

	2023					2022					2021
	Income		Shares	Per Share Amount		Income		Shares	Per Share Amount		Income		Shares	Per Share Amount
Basic earnings per share	$	418.0	87.1	$	4.80	$	1,279.1	91.1	$	14.05	$	2,377.3	96.7	$	24.60
Stock options and stock awards	—		0.5			—		0.5			—		0.8
Diluted earnings per share	$	418.0	87.6	$	4.77	$	1,279.1	91.6	$	13.97	$	2,377.3	97.5	$	24.39

The following table summarizes the potential common shares not included in the computation of diluted earnings per share because their impact would have been antidilutive:

	Years Ended December 31,
	2023	2022	2021
Stock options	0.2	0.2	0.1

Stock Options (in shares)

0.2

0.2

0.1

New Accounting Pronouncements or Change in Accounting Principle [Line Items]

Increase (Decrease) in Deferred Liabilities

$ 78,100,000

$ (26,300,000)

$ 37,300,000

Accounts receivable from Ontario government sponsored healthcare plan

$ 5,500,000