Related Party Transactions - Ashland Costs Allocated (Details) $ in Millions	12 Months Ended
	Sep. 30, 2016 USD ($)
Related Party Transaction [Line Items]
Centralized and administrative support costs	$ 79
Affiliated Entity
Related Party Transaction [Line Items]
Centralized and administrative support costs	79
Affiliated Entity | Information technology
Related Party Transaction [Line Items]
Centralized and administrative support costs	20
Affiliated Entity | Financial and accounting
Related Party Transaction [Line Items]
Centralized and administrative support costs	12
Affiliated Entity | Building services
Related Party Transaction [Line Items]
Centralized and administrative support costs	11
Affiliated Entity | Legal and environmental
Related Party Transaction [Line Items]
Centralized and administrative support costs	6
Affiliated Entity | Human resources
Related Party Transaction [Line Items]
Centralized and administrative support costs	5
Affiliated Entity | Shared services
Related Party Transaction [Line Items]
Centralized and administrative support costs	2
Affiliated Entity | Stock-based compensation
Related Party Transaction [Line Items]
Centralized and administrative support costs	11
Affiliated Entity | Other general and administrative
Related Party Transaction [Line Items]
Centralized and administrative support costs	$ 12