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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 2
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GOODWILL (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
GOODWILL (Details) - USD ($) $ in Millions	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2017
Changes to our goodwill balances by segment
Goodwill balance as of January 1, 2017			$ 3,046.2
Goodwill balance as of June 30, 2017		$ 3,053.5	3,053.5
Accumulated impairment losses		0.0	0.0
Amount of Impairment from Goodwill test		0.0
Bluewater
Changes to our goodwill balances by segment
Acquisition of Bluewater	$ 7.3		7.3
Wisconsin
Changes to our goodwill balances by segment
Goodwill balance as of January 1, 2017			2,104.3
Goodwill balance as of June 30, 2017		2,104.3	2,104.3
Wisconsin \| Bluewater
Changes to our goodwill balances by segment
Acquisition of Bluewater			0.0
Illinois
Changes to our goodwill balances by segment
Goodwill balance as of January 1, 2017			758.7
Goodwill balance as of June 30, 2017		758.7	758.7
Illinois \| Bluewater
Changes to our goodwill balances by segment
Acquisition of Bluewater			0.0
Other States
Changes to our goodwill balances by segment
Goodwill balance as of January 1, 2017			183.2
Goodwill balance as of June 30, 2017		183.2	183.2
Other States \| Bluewater
Changes to our goodwill balances by segment
Acquisition of Bluewater			0.0
Non-Utility Energy Infrastructure
Changes to our goodwill balances by segment
Goodwill balance as of January 1, 2017			0.0
Goodwill balance as of June 30, 2017		$ 7.3	7.3
Non-Utility Energy Infrastructure \| Bluewater
Changes to our goodwill balances by segment
Acquisition of Bluewater			$ 7.3