Restructuring and Related Activities (DowDupont Cost Synergy Program) (Details) - USD ($) $ in Millions	3 Months Ended							9 Months Ended		37 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	$ 617				$ 147			$ 719	$ 368
The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	617				147			719	368
DowDuPont Cost Synergy Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			$ 90	$ 33	56	$ 59	$ 144			$ 961
Restructuring Reserve, Settled without Cash				33	5	29	76
Payments for Restructuring	44	$ 22	43	56	83	73	83
Restructuring Reserve	48	96	118	71	127	159	202	48	127	48	$ 217
DowDuPont Cost Synergy Program [Member] | Accrued and Other Current Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	35			52				35		35
DowDuPont Cost Synergy Program [Member] | Other Noncurrent Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	13			19				13		13
DowDuPont Cost Synergy Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment	(4)
DowDuPont Cost Synergy Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net							1
DowDuPont Cost Synergy Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			90	26	50	37	143
DowDuPont Cost Synergy Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				5	1	22
DowDuPont Cost Synergy Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				2	5
Employee Severance [Member] | DowDuPont Cost Synergy Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			90	0	46	25	52			653
Restructuring Reserve, Accrual Adjustment	4
Restructuring Reserve, Settled without Cash				0	0	0	0
Payments for Restructuring	44	21	42	52	77	71	79
Restructuring Reserve	33	81	102	54	106	137	183	33	106	33	210
Employee Severance [Member] | DowDuPont Cost Synergy Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment	(4)
Employee Severance [Member] | DowDuPont Cost Synergy Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net							0
Employee Severance [Member] | DowDuPont Cost Synergy Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			90	0	46	25	52
Employee Severance [Member] | DowDuPont Cost Synergy Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				0	0	0
Employee Severance [Member] | DowDuPont Cost Synergy Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				0	0
Asset write-downs and write-offs [Member] | DowDuPont Cost Synergy Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			0	33	5	29	76			263
Restructuring Reserve, Settled without Cash				33	5	29	76
Payments for Restructuring	0	0	0	0	0	0	0
Restructuring Reserve	0	0	0	0	0	0	0	0	0	0	0
Asset write-downs and write-offs [Member] | DowDuPont Cost Synergy Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment	0
Asset write-downs and write-offs [Member] | DowDuPont Cost Synergy Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net							0
Asset write-downs and write-offs [Member] | DowDuPont Cost Synergy Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			0	26	4	7	76
Asset write-downs and write-offs [Member] | DowDuPont Cost Synergy Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				5	1	22
Asset write-downs and write-offs [Member] | DowDuPont Cost Synergy Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				2	0
Costs Associated with Exit and Disposal Activities [Member] | DowDuPont Cost Synergy Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			0	0	5	5	16			45
Restructuring Reserve, Settled without Cash				0	0	0	0
Payments for Restructuring	0	1	1	4	6	2	4
Restructuring Reserve	15	$ 15	16	17	21	22	19	$ 15	$ 21	$ 15	$ 7
Costs Associated with Exit and Disposal Activities [Member] | DowDuPont Cost Synergy Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Accrual Adjustment	$ 0
Costs Associated with Exit and Disposal Activities [Member] | DowDuPont Cost Synergy Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net							1
Costs Associated with Exit and Disposal Activities [Member] | DowDuPont Cost Synergy Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net			$ 0	0	0	5	$ 15
Costs Associated with Exit and Disposal Activities [Member] | DowDuPont Cost Synergy Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				0	0	$ 0
Costs Associated with Exit and Disposal Activities [Member] | DowDuPont Cost Synergy Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net				$ 0	$ 5