Utility Regulatory Assets and Liabilities and Regulatory Matters (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	$ 244.9	$ 338.4
Regulatory Liabilities	37.3	28.3
Postretirement benefits [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	16.5	13.1
Environmental overcollections [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	2.6	2.9
Deferred fuel and power refunds [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	8.3	4.4
State tax benefits - distribution system repairs [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	8.4	7.4
Other regulatory liabilities [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Liabilities	1.5	0.5
Income taxes recoverable [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	106.1	103.2
Underfunded pension and postretirement plans [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	94.5	188.2
Environmental costs [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	17.1	16.8
Deferred fuel and power costs [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	8.3	11.6
Removal costs, net [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	13.3	12.7
Other regulatory assets [Member]
Regulatory Assets and Liabilities [Line Items]
Regulatory Assets	$ 5.6	$ 5.9