Stockholders' Equity - Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance			$ (103.4)	$ 740.7
Other comprehensive loss before reclassifications			(9.2)
Net transfers from Air Products			(2.1)
Amounts reclassified from AOCL			0.3
Total Other Comprehensive Income (Loss)	$ (4.5)	$ 0.5	(11.0)	15.6
Other comprehensive loss attributable to non-controlling interest	(0.2)	(0.6)	1.2	(0.1)
Stockholders' equity, ending balance	(9.7)	$ 774.2	(9.7)	$ 774.2
Accumulated other comprehensive loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance			(10.0)
Stockholders' equity, ending balance	(22.2)		(22.2)
Net loss on derivatives qualifying as hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance			(0.2)
Other comprehensive loss before reclassifications			0.0
Net transfers from Air Products			0.0
Amounts reclassified from AOCL			0.0
Total Other Comprehensive Income (Loss)			0.0
Other comprehensive loss attributable to non-controlling interest			0.0
Stockholders' equity, ending balance	(0.2)		(0.2)
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance			(9.8)
Other comprehensive loss before reclassifications			(9.2)
Net transfers from Air Products			3.8
Amounts reclassified from AOCL			0.0
Total Other Comprehensive Income (Loss)			(5.4)
Other comprehensive loss attributable to non-controlling interest			1.2
Stockholders' equity, ending balance	(16.4)		(16.4)
Pension and postretirement benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance			0.0
Other comprehensive loss before reclassifications			0.0
Net transfers from Air Products			(5.9)
Amounts reclassified from AOCL			0.3
Total Other Comprehensive Income (Loss)			(5.6)
Other comprehensive loss attributable to non-controlling interest			0.0
Stockholders' equity, ending balance	$ (5.6)		$ (5.6)