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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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ALAGASCO ACQUISITION - Alabama Gas Corporation (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended		1 Months Ended	3 Months Ended
	Jan. 06, 2015	Sep. 02, 2014	Jan. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Sep. 02, 2014
Business Acquisition [Line Items]
Goodwill				$ 946.0us-gaap_Goodwill		$ 937.8us-gaap_Goodwill
Alagasco
Business Acquisition [Line Items]
Percentage of voting interest acquired		100.00%					100.00%
Total consideration transferred		1,600.0
Payments to acquire businesses, net of cash acquired		1,305.2	1,313.8
Final reconciliation of net assets payments to acquire businesses	8.6			8.6
Goodwill				$ 735.8	$ 727.6	$ 727.6