Goodwill and Other Intangibles - Goodwill by Reportable Segment (Details) $ in Millions	3 Months Ended
	Dec. 31, 2016 USD ($)
Goodwill
Balance at September 30, 2015	$ 665.7
Measurement period adjustment	(2.1)
Foreign currency translation	(5.6)
Balance at June 8, 2016	658.0
Chemicals
Goodwill
Balance at September 30, 2015	331.6
Measurement period adjustment	(1.3)
Foreign currency translation	(0.3)
Balance at June 8, 2016	330.0
Plastics
Goodwill
Balance at September 30, 2015	271.1
Measurement period adjustment	(0.6)
Foreign currency translation	(5.3)
Balance at June 8, 2016	265.2
Other
Goodwill
Balance at September 30, 2015	63.0
Measurement period adjustment	(0.2)
Foreign currency translation	0.0
Balance at June 8, 2016	$ 62.8