BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%	100.00%	100.00%
Total net revenues	$ 2,397	$ 2,338	$ 4,763	$ 4,669
Total operating income	355	348	655	653
Non-operating expense, net	(41)	(31)	(75)	(59)
Income before income taxes and equity in earnings of equity method investees	314	317	580	594
Income tax expense	(74)	(75)	(140)	(140)
Equity in earnings of equity method investees, net of taxes	0	7	8	12
Net income	240	249	448	466
Less: Net income attributable to noncontrolling interests	11	14	25	29
Net income attributable to Quest Diagnostics	$ 229	$ 235	$ 423	$ 437
DIS business
Segment Reporting Information [Line Items]
Percentage of net revenues	97.00%	97.00%	97.00%	97.00%
Total net revenues	$ 2,333	$ 2,268	$ 4,631	$ 4,527
Total operating income	$ 420	$ 410	$ 793	$ 784
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	$ 64	$ 70	$ 132	$ 142
Total operating income	8	10	17	18
General corporate activities
Segment Reporting Information [Line Items]
Total operating income	$ (73)	$ (72)	$ (155)	$ (149)