ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in Amounts Included in Our Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period			$ 8,731
Translation adjustments	$ (25)	$ 11	(1)	$ (14)
Total other comprehensive income	5	30	171	74
Balance at end of period	10,369	8,527	10,369	8,527
Pension
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(924)	(1,060)	(1,064)	(1,128)
Other comprehensive income (loss) before reclassifications	6	(6)	102	14
Amounts reclassified from accumulated other comprehensive loss to earnings	23	24	67	72
Total other comprehensive income	29	18	169	86
Balance at end of period	(895)	(1,042)	(895)	(1,042)
Other Post-Employment Benefits
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(10)	(11)	(12)	(12)
Other comprehensive income (loss) before reclassifications	(1)	1	(1)	1
Amounts reclassified from accumulated other comprehensive loss to earnings	2	0	4	1
Total other comprehensive income	1	1	3	2
Balance at end of period	(9)	(10)	(9)	(10)
Translation Adjustment and Other
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	278	211	254	236
Translation adjustments	(25)	11	(1)	(14)
Total other comprehensive income	(25)	11	(1)	(14)
Balance at end of period	253	222	253	222
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(656)	(860)	(822)	(904)
Total other comprehensive income	5	30	171	74
Balance at end of period	$ (651)	$ (830)	$ (651)	$ (830)