SHAREHOLDERS' INTEREST - Changes in Amounts Included in Our Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	$ 8,177	$ 9,046
Translation adjustments	18	26	$ (54)
Reclassification of certain effects due to tax law changes			253
Reclassification of accumulated unrealized gains on available-for-sale securities			(9)
Balance at end of year	8,731	8,177	9,046
Pension
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	(1,128)	(1,343)	(1,810)
Other comprehensive income (loss) before reclassifications	(223)	(216)	388
Amounts reclassified from accumulated other comprehensive income (loss) to earnings	287	431	325
Total other comprehensive income	64	215	713
Reclassification of certain effects due to tax law changes	0	0	(246)
Balance at end of year	(1,064)	(1,128)	(1,343)
Other Post-Employment Benefits
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	(12)	(19)	(25)
Other comprehensive income (loss) before reclassifications	(3)	6	13
Amounts reclassified from accumulated other comprehensive income (loss) to earnings	3	1	0
Total other comprehensive income	0	7	13
Reclassification of certain effects due to tax law changes	0	0	(7)
Balance at end of year	(12)	(12)	(19)
Translation Adjustment And Other
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	236	210	273
Translation adjustments	18	26	(54)
Total other comprehensive income	18	26	(54)
Reclassification of accumulated unrealized gains on available-for-sale securities	0	0	(9)
Balance at end of year	254	236	210
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	(904)	(1,152)	(1,562)
Total other comprehensive income	82	248	672
Balance at end of year	$ (822)	$ (904)	$ (1,152)