Restructuring and related activities (2020 Restructuring Program) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
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
2020 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	575
Restructuring Reserve, Settled without Cash	(197)
Payments for Restructuring	(1)
Restructuring Reserve	377		$ 377
2020 Restructuring Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	$ 575
restructuring and related cost, percentage	6.00%		6.00%
restructuring and related cost, percentage	6.00%		6.00%
2020 Restructuring Program [Member] | Accrued and Other Current Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 166		$ 166
2020 Restructuring Program [Member] | Other Noncurrent Obligations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	211		211
2020 Restructuring Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	11
2020 Restructuring Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	22
2020 Restructuring Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	174
2020 Restructuring Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	368
Employee Severance [Member] | 2020 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	297
Restructuring Reserve, Settled without Cash	0
Payments for Restructuring	(1)
Restructuring Reserve	296		296
Employee Severance [Member] | 2020 Restructuring Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	297
Payments for Restructuring	(1)
Employee Severance [Member] | 2020 Restructuring Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	0
Employee Severance [Member] | 2020 Restructuring Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	0
Employee Severance [Member] | 2020 Restructuring Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	0
Employee Severance [Member] | 2020 Restructuring Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	297
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	197
Restructuring Reserve, Settled without Cash	(197)
Payments for Restructuring	0
Restructuring Reserve	0		0
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	197
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	11
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Packaging & Specialty Plastics [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	11
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	22
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Industrial Intermediates & Infrastructure [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	22
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	117
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Performance Materials & Coatings [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	117
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	47
Asset write-downs and write-offs [Member] | 2020 Restructuring Program [Member] | Corporate Segment [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	47
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	81
Restructuring Reserve, Settled without Cash	0
Payments for Restructuring	0
Restructuring Reserve	81		$ 81
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	25
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	56
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | The Dow Chemical Company [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	81
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Packaging & Specialty Plastics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	0
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Industrial Intermediates & Infrastructure [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	0
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Performance Materials & Coatings [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	57
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Performance Materials & Coatings [Member] | Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	5
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Performance Materials & Coatings [Member] | Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	52
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Corporate Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	24
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Corporate Segment [Member] | Contract Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	20
Costs Associated with Exit and Disposal Activities [Member] | 2020 Restructuring Program [Member] | Corporate Segment [Member] | Environmental Remediation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and asset related charges - net	$ 4