RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)​ - Reclassifications (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net		$ 74	$ 44	$ 106	$ 35
Interest rate contracts		66	75	208	235
Costs applicable to sales	[1]	1,367	1,269	3,895	3,659
Total before tax		71	(880)	(1,615)	(2,209)
Tax		(222)	(305)	(798)	(446)
Net of tax		243	(856)	(997)	(2,027)
Loss from debt extinguishment (3)		0	0	0	(77)
Interest rate contracts
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Loss from debt extinguishment (3)			0		(8)
Reclassification Out of Accumulated Other Comprehensive Income
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Net of tax		8	72	24	91
Reclassification Out of Accumulated Other Comprehensive Income | Marketable debt securities adjustments:
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net		0	0	0	(5)
Total before tax		0	0	0	(5)
Tax		0	0	0	0
Net of tax		0	0	0	(5)
Reclassification Out of Accumulated Other Comprehensive Income | Pension and other post-retirement benefit adjustments:
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Total before tax		7	88	21	104
Tax		(1)	(19)	(3)	(22)
Net of tax		6	69	18	82
Reclassification Out of Accumulated Other Comprehensive Income | Amortization
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net		7	5	21	19
Reclassification Out of Accumulated Other Comprehensive Income | Settlements
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Other income, net		0	83	0	85
Reclassification Out of Accumulated Other Comprehensive Income | Hedge instruments adjustments:
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Total before tax		3	3	7	18
Tax		(1)	0	(1)	(4)
Net of tax		2	3	6	14
Reclassification Out of Accumulated Other Comprehensive Income | Hedge instruments adjustments: | Interest rate contracts
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Interest rate contracts		3	3	7	16
Reclassification Out of Accumulated Other Comprehensive Income | Hedge instruments adjustments: | Operating cash flow hedges
Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Costs applicable to sales		$ 0	$ 0	$ 0	$ 2

[1] Excludes Depreciation and amortization and Reclamation and remediation.