BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%	100.00%	100.00%
Total net revenues	$ 2,295	$ 2,486	$ 6,964	$ 7,550
Total operating income	342	392	995	1,293
Non-operating expense, net	(43)	(41)	(102)	(167)
Income before income taxes and equity in earnings of equity method investees	299	351	893	1,126
Income tax expense	(68)	(81)	(208)	(268)
Equity in earnings of equity method investees, net of taxes	6	6	18	41
Net income	237	276	703	899
Less: Net income attributable to noncontrolling interests	12	20	41	54
Net income attributable to Quest Diagnostics	$ 225	$ 256	$ 662	$ 845
Total net revenues, percent	100.00%	100.00%	100.00%	100.00%
Routine clinical testing services
Segment Reporting Information [Line Items]
Total net revenues, percent	51.00%	45.00%	50.00%	43.00%
COVID-19 Testing Services
Segment Reporting Information [Line Items]
Total net revenues, percent	1.00%	13.00%	3.00%	17.00%
Gene-based and esoteric testing services
Segment Reporting Information [Line Items]
Total net revenues, percent	39.00%	33.00%	38.00%	31.00%
Anatomic pathology testing services
Segment Reporting Information [Line Items]
Total net revenues, percent	6.00%	6.00%	6.00%	6.00%
All other services
Segment Reporting Information [Line Items]
Total net revenues, percent	3.00%	3.00%	3.00%	3.00%
DIS business
Segment Reporting Information [Line Items]
Percentage of net revenues	97.00%	97.00%	97.00%	97.00%
Total net revenues	$ 2,228	$ 2,419	$ 6,755	$ 7,344
Total operating income	$ 392	$ 441	$ 1,176	$ 1,445
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	$ 67	$ 67	$ 209	$ 206
Total operating income	8	3	26	16
General corporate activities
Segment Reporting Information [Line Items]
Total operating income	$ (58)	$ (52)	$ (207)	$ (168)

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