Commitments, Contingencies and Litigation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Environmental Remediation
Rent expense	$ 6.4	$ 6.2
Ashland
Environmental Remediation
Total indemnification obligation under the purchase agreement (other than for liabilities relating to taxes or any retained indebtedness)	139.5
Ashland | Other Retained Remediation Liabilities
Environmental Remediation
Remediation indemnification obligation resulting from breach of any representation, warranty or covenant individual claim threshold	0.2
Remediation indemnification obligation resulting from breach of any representation, warranty or covenant aggregate claim deductible	5.0
Ashland | Retained Remediation Liabilities
Environmental Remediation
Remediation indemnification obligation resulting from breach of any representation, warranty or covenant ceiling amount	75.0
Ashland | Breach of representation, warranty or covenant, related to environmental matters
Environmental Remediation
Remediation indemnification obligation resulting from breach of any representation, warranty or covenant individual claim threshold	0.2
Remediation indemnification obligation resulting from breach of any representation, warranty or covenant aggregate claim deductible	18.6
Remediation indemnification obligation resulting from breach of any representation, warranty or covenant ceiling amount	$ 93.0