GOODWILL AND OTHER INTANGIBLE ASSETS - Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 8 months 12 days
Cost	$ 770	$ 753
Accumulated Amortization	544	473
Net	$ 226	280
Customer contracts/relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 9 months 18 days
Cost	$ 566	566
Accumulated Amortization	401	347
Net	$ 165	219
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 2 months 12 days
Cost	$ 104	104
Accumulated Amortization	84	69
Net	$ 20	35
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	11 years 10 months 24 days
Cost	$ 68	51
Accumulated Amortization	30	29
Net	$ 38	22
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 1 month 6 days
Cost	$ 32	32
Accumulated Amortization	29	28
Net	$ 3	$ 4