BUSINESS ACQUISITIONS - Pro Forma (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2024
Business Combination [Abstract]
Pro forma net revenues	$ 2,588	$ 7,700
Pro forma net income attributable to Quest Diagnostics	$ 222	$ 647
Pro forma earnings per share attributable to Quest Diagnostics' common stockholders:
Basic (in dollars per share)	$ 1.97	$ 5.78
Diluted (in dollars per share)	$ 1.95	$ 5.72

Business Acquisition, Pro Forma Earnings Per Share, Basic and Diluted [Abstract]

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Per basic share amount, after tax, of pro forma income (loss) of combined entity as if acquisition date of business combination occurred as of beginning of period.

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