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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period			$ 8,177
Translation adjustments	$ 11	$ (6)	(14)	$ 19
Total other comprehensive income	30	19	74	416
Balance at end of period	8,527	8,599	8,527	8,599
Pension
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(1,060)	(972)	(1,128)	(1,343)
Other comprehensive income (loss) before reclassifications	(6)	4	14	(10)
Amounts reclassified from accumulated other comprehensive loss to earnings	24	21	72	406
Total other comprehensive income	18	25	86	396
Balance at end of period	(1,042)	(947)	(1,042)	(947)
Other Postretirement Benefits
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(11)	(18)	(12)	(19)
Other comprehensive income (loss) before reclassifications	1	0	1	0
Amounts reclassified from accumulated other comprehensive loss to earnings	0	0	1	1
Total other comprehensive income	1	0	2	1
Balance at end of period	(10)	(18)	(10)	(18)
Translation Adjustment and Other
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	211	235	236	210
Translation adjustments	11	(6)	(14)	19
Total other comprehensive income	11	(6)	(14)	19
Balance at end of period	222	229	222	229
Accumulated other comprehensive loss:
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(860)	(755)	(904)	(1,152)
Total other comprehensive income	30	19	74	416
Balance at end of period	$ (830)	$ (736)	$ (830)	$ (736)