Restructuring and Related Activities (DowDupont Cost Synergy Program) (Details) - USD ($) $ in Millions	3 Months Ended						6 Months Ended		34 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	$ 6				$ 65		$ 102	$ 221
The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	6				65		102	221
DowDuPont Cost Synergy Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	96	$ 118	$ 71	$ 127	159	$ 202	96	159	$ 96	$ 217
Restructuring and asset related charges - net		90	33	56	59	144			965
Restructuring Reserve, Settled without Cash			33	5	29	76
Payments for Restructuring	22	43	56	83	73	83
DowDuPont Cost Synergy Program [Member] | Accrued and Other Current Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	83		52				83		83
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] | 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 Reserve	81	102	54	106	137	183	81	137	81	210
Restructuring and asset related charges - net		90	0	46	25	52			657
Restructuring Reserve, Settled without Cash			0	0	0	0
Payments for Restructuring	21	42	52	77	71	79
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 Reserve	0	0	0	0	0	0	0	0	0	0
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
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 Reserve	15	16	17	21	22	19	$ 15	$ 22	15	$ 7
Restructuring and asset related charges - net		0	0	5	5	16			$ 45
Restructuring Reserve, Settled without Cash			0	0	0	0
Payments for Restructuring	$ 1	1	4	6	2	4
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