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FAIR VALUE MEASUREMENTS - Summary of Financial Instruments at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	$ 412	$ 283	$ 256	$ 561
Short-term investments	385	157
Net derivative contracts	33	14
Level 1
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	412	283
Short-term investments	385	157
Net derivative contracts	0	0
Level 2
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	0	0
Short-term investments	0	0
Net derivative contracts	33	14
Level 3
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Cash	0	0
Short-term investments	0	0
Net derivative contracts	$ 0	$ 0