FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Liabilities:
Highly liquid investments, maturity period (in months)	3 months
Recurring basis
Assets:
Cash equivalents	$ 263	$ 197
Restricted cash	2	2
Liabilities:
Acquisition-related contingent consideration	309	339
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	235	166
Restricted cash	2	2
Liabilities:
Acquisition-related contingent consideration	0	0
Recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	28	31
Restricted cash	0	0
Liabilities:
Acquisition-related contingent consideration	0	0
Recurring basis | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Restricted cash	0	0
Liabilities:
Acquisition-related contingent consideration	$ 309	$ 339
Minimum | Measurement Input, Discount Rate | Recurring basis | Significant Unobservable Inputs (Level 3)
Liabilities:
Fair value, contingent consideration obligations, discount rate	0.05
Maximum | Measurement Input, Discount Rate | Recurring basis | Significant Unobservable Inputs (Level 3)
Liabilities:
Fair value, contingent consideration obligations, discount rate	0.25