INVESTMENTS IN EQUITY INVESTEES - SCHEDULE OF COST METHOD INVESTMENTS (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014 Two Dot Wind Project in Montana [Member] MW	Mar. 31, 2014 Carroll Wind Project in Iowa [Member] MW	Sep. 30, 2012 OwnEnergy [Member]
Schedule of Cost-method Investments [Line Items]
Cost method investments	$ 22.0	$ 42.0	$ 8.8
Cost method investment, ownership percentage			18.70%
Number of megawatts	9.7	20

Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6872867&loc=d3e40691-111596

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 325

-SubTopic 20

-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=29638308&loc=d3e40346-111594

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