Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales	$ 10,204	$ 10,764	$ 11,014	$ 10,969	$ 11,944	$ 12,634	$ 12,789	$ 12,237	$ 42,951	$ 49,604	$ 43,730
Cost of sales	8,718	9,377	9,420	9,142	10,098	10,456	10,540	9,980	36,657	41,074	36,350
Research and development expenses									765	800	803
Selling, general and administrative expenses									1,590	1,782	1,795
Amortization of intangibles									419	469	400
Restructuring, goodwill impairment and asset related charges - net	2,851	147	65	156	46	48	40	87	3,219	221	2,739
Integration and separation costs	99	164	348	452	380	313	262	224	1,063	1,179	798
Equity in earnings (losses) of nonconsolidated affiliates									(94)	555	394
Sundry income (expense) - net									461	96	(154)
Interest income									81	82	66
Interest expense and amortization of debt discount									933	1,063	914
Income (loss) from continuing operations before income taxes									(1,247)	3,749	237
Provision for income taxes on continuing operations									470	809	1,524
Income (loss) from continuing operations, net of tax	(2,310)	347	90	156	491	714	810	925	(1,717)	2,940	(1,287)
Income from discontinued operations, net of tax	0	0	0	445	432	335	554	514	445	1,835	1,882
Net income (loss)	(2,310)	347	90	601	923	1,049	1,364	1,439	(1,272)	4,775	595
Net income attributable to noncontrolling interests									87	134	130
Net income (loss) available for Dow Inc. common stockholders	$ (2,323)	$ 333	$ 75	$ 556	$ 891	$ 1,013	$ 1,333	$ 1,404	$ (1,359)	$ 4,641	$ 465
Earnings (loss) per common share from continuing operations - basic	$ (3.14)	$ 0.45	$ 0.10	$ 0.16	$ 0.63	$ 0.91	$ 1.05	$ 1.21	$ (2.42)	$ 3.80	$ (1.88)
Earnings per common share from discontinued operations - basic									0.58	2.41	2.48
Earnings (loss) per common share - basic									(1.84)	6.21	0.60
Earnings (loss) per common share from continuing operations - diluted	$ (3.14)	$ 0.45	$ 0.10	$ 0.16	$ 0.63	$ 0.91	$ 1.05	$ 1.21	(2.42)	3.80	(1.88)
Earnings per common share from discontinued operations - diluted									0.58	2.41	2.48
Earnings (loss) per common share - diluted									$ (1.84)	$ 6.21	$ 0.60
Weighted-average common shares outstanding - basic									742.5	747.2	744.8
Weighted-average common shares outstanding - diluted									742.5	747.2	744.8