Quarterly Operating Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Net revenues	$ 1,861	$ 1,885	$ 1,906	$ 1,863	$ 1,849	$ 1,880	$ 1,925	$ 1,839	$ 7,515	$ 7,493	$ 7,435
Gross profit	701	728	751	719	699	718	743	676	2,899	2,836
Income from continuing operations	167	205	209	115	200	354	129	70	696	753	587
Income (loss) from discontinued operations, net of taxes	0	0	0	0	0	0	0	0	0	0	5
Net income	167	205	209	115	200	354	129	70	696	753	592
Less: net income attributable to noncontrolling interests	12	13	14	12	12	12	11	9	51	44	36
Net income attributable to Quest Diagnostics	155	192	195	103	188	342	118	61	645	709	556
Income from continuing operations	$ 155	$ 192	$ 195	$ 103	$ 188	$ 342	$ 118	$ 61	$ 645	$ 709	$ 551
Income from continuing operations	$ 1.11	$ 1.37	$ 1.38	$ 0.72	$ 1.31	$ 2.37	$ 0.82	$ 0.42	$ 4.58	$ 4.92	$ 3.80
Income (loss) from discontinued operations, per basic share	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.03
Net income	1.11	1.37	1.38	0.72	1.31	2.37	0.82	0.42	4.58	4.92	3.83
Income from continuing operations	1.09	1.34	1.37	0.71	1.29	2.35	0.81	0.42	4.51	4.87	3.78
Income (loss) from discontinued operations, per diluted share	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.03
Net income	$ 1.09	$ 1.34	$ 1.37	$ 0.71	$ 1.29	$ 2.35	$ 0.81	$ 0.42	$ 4.51	$ 4.87	$ 3.81