Restructuring and Other Charges (2018 Actions) - Additional Information (Detail) € in Millions, $ in Millions	1 Months Ended		3 Months Ended		12 Months Ended
	Jan. 31, 2018 USD ($)	Jan. 31, 2018 EUR (€)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) Potline kt	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 138	$ 297	$ 527	$ 309	$ 318
Settlements and/or curtailments related to retirement benefits					331	8	17
Allowance on value-added tax credits					107
Litigation settlement	$ 18	€ 15			8
Cash payment					102	73	109
Asset impairments					18	40	$ 155
Asset retirement obligations					63	$ 70
2018 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					527
Settlements and/or curtailments related to retirement benefits					331
Litigation settlement					23
Brazil [Member] | 2018 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Allowance on value-added tax credits					107
Contract Termination [Member] | 2018 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					86
Net benefit					15
Additional restructuring charge					73
Cash payment					$ 62
Total number of potlines | Potline					4
Number of potlines closed | Potline					1
Capacity closure | kt					38
Asset impairments					$ 10
Asset retirement obligations					$ 1
Remaining number of potlines | Potline					3
Remaining curtailment capacity | kt					146
Other Adjustments [Member] | 2018 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Net benefit					$ 38
Other Item Charges [Member] | 2018 Restructuring Plans Action [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges					$ 18