CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 591	$ 226	$ 890	$ 641
Other comprehensive income (loss):
Foreign currency translation adjustment	10	(6)	(6)	(6)
Net change in available-for-sale debt securities, net of taxes	0	8	0	8
Net deferred gain on cash flow hedges, net of taxes	3	1	3	2
Other comprehensive income (loss)	13	3	(3)	4
Comprehensive income	604	229	887	645
Less: Comprehensive income attributable to noncontrolling interests	23	11	38	36
Comprehensive income attributable to Quest Diagnostics	$ 581	$ 218	$ 849	$ 609