GOODWILL AND OTHER INTANGIBLE ASSETS - Intangible Assets Included in Other Long-Term Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 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	718	652
Net	$ 352	177
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 6 months
Cost	$ 849	646
Accumulated Amortization	553	496
Net	$ 296	150
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	7 years
Cost	$ 122	84
Accumulated Amortization	87	84
Net	$ 35	0
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	11 years 9 months 18 days
Cost	$ 70	70
Accumulated Amortization	49	44
Net	$ 21	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