Certain Balance Sheet Information - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Jun. 09, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Line of Credit Facility [Line Items]
Cash and cash equivalents		$ 43.8		$ 43.8		$ 53.9
Nexeo Solutions Inc.
Line of Credit Facility [Line Items]
Excess shares (in shares)		5,178,642		5,178,642
Number of days to elect excess shares provision	5 days
Contingent consideration - Fair value of deferred cash consideration		$ 46.3		$ 46.3		35.1
Payment by the company to selling equityholders of percentage of net cash tax savings	85.00%
Percentage of net cash tax savings retained by the Company	15.00%
Contingent consideration - current undiscounted cash flows of TRA liability				$ 134.5
Expected benefit period of TRA				20 years
Contingent consideration - Fair value of TRA		75.0		$ 75.0		$ 105.1
ABL Facility
Line of Credit Facility [Line Items]
Amortization of debt issuance costs		$ 0.4	$ 0.7	$ 1.0	$ 1.0
Selling equityholders | Nexeo Solutions Inc.
Line of Credit Facility [Line Items]
Number of trading days to meet condition one	20 days
Number of consecutive trading days	30 days
Share price (USD per share)	$ 15.00