BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%	100.00%	100.00%
Total net revenues	$ 2,338	$ 2,453	$ 4,669	$ 5,064
Total operating income	348	388	653	901
Non-operating expense, net	(31)	(65)	(59)	(126)
Income before income taxes and equity in earnings of equity method investees	317	323	594	775
Income tax expense	(75)	(77)	(140)	(187)
Equity in earnings of equity method investees, net of taxes	7	4	12	35
Net income	249	250	466	623
Less: Net income attributable to noncontrolling interests	14	16	29	34
Net income attributable to Quest Diagnostics	$ 235	$ 234	$ 437	$ 589
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	2.00%	14.00%	3.00%	19.00%
Gene-based and esoteric testing services
Segment Reporting Information [Line Items]
Total net revenues, percent	38.00%	32.00%	37.00%	30.00%
Anatomic pathology testing services
Segment Reporting Information [Line Items]
Total net revenues, percent	6.00%	6.00%	7.00%	5.00%
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	$ 2,268	$ 2,384	$ 4,527	$ 4,925
Total operating income	$ 410	$ 442	$ 784	$ 1,004
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	$ 70	$ 69	$ 142	$ 139
Total operating income	10	6	18	13
General corporate activities
Segment Reporting Information [Line Items]
Total operating income	$ (72)	$ (60)	$ (149)	$ (116)

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