Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit (costs) credits	$ (6)			$ 2			$ 1	$ 9
Net gain on disposal of assets	1			22			8	56
Net income (loss)	(317)	$ (750)	$ (46)	165	$ 161	$ 174	(1,113)	500
Amortization of prior service credit | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit (costs) credits	5			6			18	19
Amortization of actuarial loss | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit (costs) credits	(2)			(3)			(8)	(7)
Net settlement loss | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit (costs) credits	(9)			0			(25)	(2)
Net curtailment gain | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit (costs) credits	0			0			17	0
Postretirement and postemployment plans | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other net periodic benefit (costs) credits	(6)			3			2	10
Net income (loss)	(6)			70			2	77
U.K. pension plan transferred to buyer (a)(b) | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on disposal of assets	0			83			0	83
Foreign currency translation adjustment related to sale of U.K. business (b) | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on disposal of assets	0			30			0	30
Income taxes related to the sale of U.K. business (b) | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on disposal of assets	0			(46)			0	(46)
Other | Reclassification out of Accumulated Other Comprehensive Income (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on disposal of assets	$ 0			$ 67			$ 0	$ 67