GOODWILL AND OTHER INTANGIBLE ASSETS - Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 8 months
Cost	$ 827	$ 770
Accumulated Amortization	564	544
Net	$ 263	226
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 8 months
Cost	$ 646	566
Accumulated Amortization	419	401
Net	$ 227	165
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	6 years 5 months
Cost	$ 84	104
Accumulated Amortization	82	84
Net	$ 2	20
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	11 years 11 months
Cost	$ 68	68
Accumulated Amortization	36	30
Net	$ 32	38
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	7 years 4 months
Cost	$ 29	32
Accumulated Amortization	27	29
Net	$ 2	$ 3