SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net revenues	$ 1,889	$ 1,856	$ 5,692	$ 5,537
Selling, general and administrative expenses	354	348	1,068	1,061
Net income attributable to Quest Diagnostics	213	161	609	518
Provision for doubtful accounts			2	5
Accounts receivable			(166)	(29)
Accounts receivable					$ 937
Allowance for doubtful accounts	10		10		13
Accounts receivable, net of allowance for doubtful accounts	$ 1,097		$ 1,097		924
Adjustments for New Accounting Pronouncement [Member] | As Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net revenues		1,931		5,773
Selling, general and administrative expenses		423		1,297
Net income attributable to Quest Diagnostics		161		518
Provision for doubtful accounts				241
Accounts receivable				(265)
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		(75)		(236)
Selling, general and administrative expenses		(75)		(236)
Net income attributable to Quest Diagnostics		$ 0		0
Provision for doubtful accounts				(236)
Accounts receivable				$ 236
Accounts receivable					(256)
Allowance for doubtful accounts					(256)
Accounts receivable, net of allowance for doubtful accounts					$ 0