BUSINESS SEGMENT INFORMATION (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Percentage of net revenues	100.00%	100.00%
Total net revenues	$ 2,652	$ 2,366
Segment operating income	346	300
Non-operating expense, net	(70)	(34)
Income before income taxes and equity in earnings of equity method investees	276	266
Income tax expense	(59)	(66)
Equity in earnings of equity method investees, net of taxes	18	8
Net income	235	208
Less: Net income attributable to noncontrolling interests	15	14
Net income attributable to Quest Diagnostics	220	194
Depreciation and amortization	$ 140	$ 116
DIS business
Segment Reporting Information [Line Items]
Percentage of net revenues	98.00%	97.00%
Total net revenues	$ 2,589	$ 2,298
Less: Other segment items	2,175	1,925
Segment operating income	414	373
Depreciation and amortization	97	84
All other operating segments
Segment Reporting Information [Line Items]
Total net revenues	63	68
Segment operating income	8	9
Depreciation and amortization	4	3
General corporate activities
Segment Reporting Information [Line Items]
Segment operating income	(76)	(82)
Depreciation and amortization	$ 39	$ 29
Minimum | DIS business
Segment Reporting Information [Line Items]
Percentage of net revenues	95.00%	95.00%