GOODWILL AND OTHER INTANGIBLE ASSETS - Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 8 months 12 days
Cost	$ 827	$ 770
Accumulated Amortization	582	544
Net	$ 245	226
Customer contracts/relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 8 months 12 days
Cost	$ 646	566
Accumulated Amortization	434	401
Net	$ 212	165
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	6 years 4 months 24 days
Cost	$ 84	104
Accumulated Amortization	83	84
Net	$ 1	20
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	11 years 9 months 18 days
Cost	$ 68	68
Accumulated Amortization	37	30
Net	$ 31	38
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	7 years 3 months 18 days
Cost	$ 29	32
Accumulated Amortization	28	29
Net	$ 1	$ 3