Restructuring Activities - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring reserve	$ 14	$ 43
Asset impairment charges	8	16
Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve	7	36
Facility Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve	7	7
Restructuring costs	7	9
Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Asset impairment charges		16
Selling, General and Administrative Expenses [Member] | Facility Costs [Member]
Restructuring Cost And Reserve [Line Items]
Asset impairment charges		12
Voluntary Severance Offer [Member] | Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs	6	$ 36
Plant Restructuring [Member] | Severance Costs [Member] | Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	5
Plant Restructuring [Member] | Accelerated Depreciation And Amortization | Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	38
Plant Restructuring [Member] | Plant Closure Costs [Member] | Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve	2
Restructuring costs	4
Plant Restructuring [Member] | Cost of Sales [Member] | Specialty Ingredients [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 47