Stock Holders Equity Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	$ (103.4)	$ 740.7	$ 873.4
Other comprehensive loss before reclassifications	(5.0)
Net transfers from Air Products	(2.4)
Amounts reclassified from AOCL	0.3
Total Other Comprehensive Income (Loss)	(7.1)	22.8	(48.4)
Other Comprehensive Loss Attributable to Non-controlling Interests	1.3	0.0	(2.1)
Stockholders' equity, ending balance	24.6	(103.4)	$ 740.7
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Stockholders' equity, beginning balance	(10.0)
Stockholders' equity, ending balance	(18.4)	(10.0)
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 Interests	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	(8.7)
Net transfers from Air Products	3.8
Amounts reclassified from AOCL	0.0
Total Other Comprehensive Income (Loss)	(4.9)
Other Comprehensive Loss Attributable to Non-controlling Interests	1.3
Stockholders' equity, ending balance	(16.0)	(9.8)
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	3.7
Net transfers from Air Products	(6.2)
Amounts reclassified from AOCL	0.3
Total Other Comprehensive Income (Loss)	(2.2)
Other Comprehensive Loss Attributable to Non-controlling Interests	0.0
Stockholders' equity, ending balance	$ (2.2)	$ 0.0