| LEASES - Supplemental Cash Flow Disclosures (Details) - USD ($) $ in Millions | 9 Months Ended | |
|---|---|---|
| Sep. 30, 2021 | Sep. 30, 2020 | |
| Leases [Abstract] | ||
| Operating cash flows from operating leases | $ 538 | $ 508 | 
| Operating cash flows from finance leases | 8 | 11 | 
| Financing cash flows from finance leases | 48 | 136 | 
| Operating leases | 953 | 544 | 
| Finance leases | $ 252 | $ 50 | 
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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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- Definition Amount of cash outflow for principal payment on finance lease. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- References No definition available. 
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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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- Definition Amount of increase in right-of-use asset obtained in exchange for finance lease liability. Reference 1: http://www.xbrl.org/2003/role/exampleRef 
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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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