BUSINESS ACQUISITIONS (Details) - USD ($) $ in Millions			3 Months Ended		6 Months Ended
	Jun. 18, 2018	Feb. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Cash acquired from acquisition			$ 0	$ 0	$ 5	$ 0
Goodwill			6,414		$ 6,414		$ 6,335	$ 6,000
Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets, useful life					18 years
Mobile Medical Examination Services, Inc. (MedXM) [Member]
Business Acquisition [Line Items]
Consideration		$ 142
Cash acquired from acquisition		5
Cash paid for acquisition		130
Contingent consideration, liability		12
Intangible assets		77
Goodwill		57
Goodwill, expected tax deductible amount		45
Working capital		7
Property, plant and equipment		1
Mobile Medical Examination Services, Inc. (MedXM) [Member] | Other Operating Income [Member]
Business Acquisition [Line Items]
Loss due to remeasure			1
Mobile Medical Examination Services, Inc. (MedXM) [Member] | Fair Value, Inputs, Level 3 [Member]
Business Acquisition [Line Items]
Contingent consideration, liability		$ 12	$ 13		$ 13
Mobile Medical Examination Services, Inc. (MedXM) [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets, useful life		15 years
Cape Cod Healthcare, Inc. [Member]
Business Acquisition [Line Items]
Cash paid for acquisition	$ 35