Income Taxes - Deferred Tax Liabilities (Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Excess book basis over tax basis of property, plant and equipment	$ 798.4	$ 675.7
Investment in AmeriGas Partners	321.4	325.1
Intangible assets and goodwill	87.1	53.0
Utility regulatory assets	117.4	110.0
Foreign currency translation adjustment	0.1	0.0
Other	8.8	3.5
Gross deferred tax liabilities	1,333.2	1,167.3
Pension plan liabilities	(59.1)	(40.6)
Employee-related benefits	(57.6)	(48.8)
Operating loss carryforwards	(32.5)	(27.9)
Foreign tax credit carryforwards	(113.8)	(47.8)
Utility regulatory liabilities	(24.0)	(14.8)
Foreign currency translation adjustment	0.0	(14.1)
Derivative instruments	(11.4)	(11.0)
Other	(23.4)	(13.0)
Gross deferred tax assets	(321.8)	(218.0)
Deferred tax assets valuation allowance	131.3	59.2
Net deferred tax liabilities	$ 1,142.7	$ 1,008.5