BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%	100.00%	100.00%
Total net revenues	$ 2,488	$ 2,295	$ 7,251	$ 6,964
Total operating income	330	342	985	995
Non-operating expense, net	(34)	(43)	(109)	(102)
Income before income taxes and equity in earnings of equity method investees	296	299	876	893
Income tax expense	(65)	(68)	(205)	(208)
Equity in earnings of equity method investees, net of taxes	6	6	14	18
Net income	237	237	685	703
Less: Net income attributable to noncontrolling interests	11	12	36	41
Net income attributable to Quest Diagnostics	$ 226	$ 225	$ 649	$ 662
DIS business
Segment Reporting Information [Line Items]
Percentage of net revenues	97.00%	97.00%	97.00%	97.00%
Total net revenues	$ 2,427	$ 2,228	$ 7,058	$ 6,755
Total operating income	$ 407	$ 392	$ 1,200	$ 1,176
DIS business | Minimum
Segment Reporting Information [Line Items]
Percentage of net revenues	95.00%	95.00%	95.00%	95.00%
All other operating segments
Segment Reporting Information [Line Items]
Total net revenues	$ 61	$ 67	$ 193	$ 209
Total operating income	6	8	23	26
General corporate activities
Segment Reporting Information [Line Items]
Total operating income	$ (83)	$ (58)	$ (238)	$ (207)