CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net revenues	$ 1,956	$ 1,889	$ 5,800	$ 5,692
Operating costs and expenses and other operating income:
Cost of services	1,264	1,222	3,773	3,691
Selling, general and administrative	362	354	1,108	1,068
Amortization of intangible assets	23	22	72	66
Other operating income, net	(6)	(13)	(21)	(14)
Total operating costs and expenses, net	1,643	1,585	4,932	4,811
Operating income	313	304	868	881
Other income (expense):
Interest expense, net	(44)	(41)	(133)	(124)
Other income, net	1	3	13	2
Total non-operating expenses, net	(43)	(38)	(120)	(122)
Income from continuing operations before income taxes and equity in earnings of equity method investees	270	266	748	759
Income tax expense	(62)	(48)	(175)	(142)
Equity in earnings of equity method investees, net of taxes	18	9	48	32
Income from continuing operations	226	227	621	649
Income from discontinued operations, net of taxes	0	0	20	0
Net income	226	227	641	649
Less: Net income attributable to noncontrolling interests	11	14	36	40
Net income attributable to Quest Diagnostics	215	213	605	609
Amounts attributable to Quest Diagnostics’ common stockholders:
Income from continuing operations	215	213	585	609
Income from discontinued operations, net of taxes	0	0	20	0
Net income attributable to Quest Diagnostics	$ 215	$ 213	$ 605	$ 609
Earnings per share attributable to Quest Diagnostics’ common stockholders - basic:
Income from continuing operations (in dollars per share)	$ 1.59	$ 1.56	$ 4.33	$ 4.46
Income from discontinued operations (in dollars per share)	0	0	0.15	0
Net income (in dollars per share)	1.59	1.56	4.48	4.46
Earnings per share attributable to Quest Diagnostics’ common stockholders - diluted:
Income from continuing operations (in dollars per share)	1.56	1.53	4.27	4.37
Income from discontinued operations (in dollars per share)	0	0	0.15	0
Net income (in dollars per share)	$ 1.56	$ 1.53	$ 4.42	$ 4.37
Weighted average common shares outstanding:
Basic (in Shares)	135	136	135	136
Diluted (in Shares)	137	139	136	139