SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net revenues	$ 1,884	$ 1,817
Selling, general and administrative expenses	363	355
Net income attributable to Quest Diagnostics	177	164
Provision for doubtful accounts	3	2
Accounts receivable	(97)	(35)
Accounts receivable			$ 932
Allowance for doubtful accounts	6		8
Accounts receivable, net of allowance for doubtful accounts	$ 1,026		924
Adjustments for New Accounting Pronouncement [Member] | As Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net revenues		1,899
Selling, general and administrative expenses		437
Net income attributable to Quest Diagnostics		164
Provision for doubtful accounts		84
Accounts receivable		(117)
Accounts receivable			1,193
Allowance for doubtful accounts			269
Accounts receivable, net of allowance for doubtful accounts			924
Adjustments for New Accounting Pronouncement [Member] | Adjustment for ASU on Revenue Recognition [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net revenues		(82)
Selling, general and administrative expenses		(82)
Net income attributable to Quest Diagnostics		0
Provision for doubtful accounts		(82)
Accounts receivable		$ 82
Accounts receivable			(261)
Allowance for doubtful accounts			(261)
Accounts receivable, net of allowance for doubtful accounts			$ 0