GOODWILL AND OTHER INTANGIBLE ASSETS - Intangible Assets Included in Other Long-Term Assets (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 3 months 18 days
Cost	$ 1,070	$ 829
Accumulated Amortization	696	652
Net	$ 374	177
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 6 months
Cost	$ 849	646
Accumulated Amortization	534	496
Net	$ 315	150
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	7 years
Cost	$ 122	84
Accumulated Amortization	86	84
Net	$ 36	0
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	11 years 9 months 18 days
Cost	$ 70	70
Accumulated Amortization	47	44
Net	$ 23	26
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	7 years 3 months 18 days
Cost	$ 29	29
Accumulated Amortization	29	28
Net	$ 0	$ 1