ACQUISITIONS - Fair Value of MGE Assets Acquired and Liabilities Assumed (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 01, 2013
Assets:
Goodwill	$ 937.8	$ 247.1
Missouri Gas Energy (MGE)
Assets:
Utility plant			671.1
Other property and investments			3.3
Goodwill	210.2	247.1	210.2
Other Property and Investments			884.6
Accounts receivable and other current assets			36.0
Inventories			62.7
Total Current Assets			983.3
Deferred Charges:
Regulatory assets			81.4
Other			14.3
Total Deferred Charges			95.7
Total Assets Acquired			1,079.0
Liabilities:
Accounts payable			19.8
Taxes accrued			17.2
Other			28.9
Total Current Liabilities			65.9
Pension and postretirement benefit costs			24.5
Asset retirement obligations			32.1
Other			16.3
Total Deferred Credits and Other Liabilities			72.9
Total Liabilities Assumed			138.8
Net Assets Acquired			$ 940.2