| LEASES - Supplemental Cash Flow Disclosures (Details) $ in Millions | 3 Months Ended | 
|---|---|
| Mar. 31, 2019  USD ($) | |
| Leases [Abstract] | |
| Operating cash flows from operating leases | $ 153 | 
| Operating cash flows from finance leases | 2 | 
| Financing cash flows from finance leases | 4 | 
| Operating leases | $ 34 | 
| X | ||||||||||
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- Definition Amount of interest paid on finance lease liability. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
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- Definition Amount of cash outflow for principal payment on finance lease. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
 | 
| X | ||||||||||
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- References No definition available. 
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| X | ||||||||||
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- Definition Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
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- Definition Amount of increase in right-of-use asset obtained in exchange for operating lease liability. Reference 1: http://www.xbrl.org/2003/role/exampleRef 
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