Significant Accounting Policies (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Accounting Policies [Abstract]
Ownership interests in certain subsidiaries under equity method investment		100% or Less
Ownership interests in certain subsidiaries under equity method investment, maximum		100.00%
Voting rights in investment businesses not traded publicly accounted for under the cost method		20% or Less
Interest (income) expense on tax deficiencies and penalties		$ 0	$ (0.1)	$ 0.2
Antidilutive outstanding stock option award		88,000	81,000	3,700,000
Maturities Period of highly liquid investments		three months or less
Estimated maximum period of capitalized and amortized costs to install partnership and antargaz-owned tanks		10 years
Maximum period of benefit for computer software amortization expense		15 years
Other-than-temporary impairment of an investment in a private equity partnership pre-tax loss	6.3	6.3	0	0
Net deferred debt issuance costs	39.4	39.4	46.6
Foreign subsidiary customer deposits	214.6	214.6	205.1
Average to Include Prudently Incurred Remediation Costs		5 years
Property, Plant and Equipment [Line Items]
Voting rights in investment businesses not traded publicly accounted for under the cost method, maximum		20.00%
Investments in other assets	82.0	82.0	80.0
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		15 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		40 years
Storage and customer tanks and cylinders [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		7 years
Storage and customer tanks and cylinders [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		40 years
Electric Utility [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense as percentage of related average depreciable base		2.40%	2.40%	2.60%
Electric Generation, Transmission and Distribution Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		25 years
Electric Generation, Transmission and Distribution Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		35 years
Vehicles, equipment and office furniture and fixtures [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		2 years
Vehicles, equipment and office furniture and fixtures [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life (in years)		12 years
Gas Utility [Member]
Property, Plant and Equipment [Line Items]
Depreciation expense as percentage of related average depreciable base		2.30%	2.20%	2.30%
Private Equity Partnership That Invests in Renewable Energy Companies [Member]
Property, Plant and Equipment [Line Items]
Voting rights in investment businesses not traded publicly accounted for under the cost method, maximum		3.50%
Investments in other assets	$ 16.4	$ 16.4	$ 20.0