CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 527	$ 591	$ 1,667	$ 890
Other comprehensive income (loss):
Foreign currency translation adjustment	(4)	10	14	(6)
Net change in available-for-sale debt securities, net of taxes	0	0	(7)	0
Net deferred gain on cash flow hedges, net of taxes	1	3	1	3
Other comprehensive (loss) income	(3)	13	8	(3)
Comprehensive income	524	604	1,675	887
Less: Comprehensive income attributable to noncontrolling interests	22	23	62	38
Comprehensive income attributable to Quest Diagnostics	$ 502	$ 581	$ 1,613	$ 849