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Derivative Instruments (Details)	9 Months Ended
	Sep. 30, 2018
Electricity (In MWH) [Member] | October 2018 [Member]
Derivative [Line Items]
Volume	96,960
Electricity (In MWH) [Member] | November 2018 [Member]
Derivative [Line Items]
Volume	68,880
Electricity (In MWH) [Member] | December 2018 [Member]
Derivative [Line Items]
Volume	86,800
Electricity (In MWH) [Member] | January 2019 [Member]
Derivative [Line Items]
Volume	173,360
Electricity (In MWH) [Member] | February 2019 [Member]
Derivative [Line Items]
Volume	157,120
Electricity (In MWH) [Member] | March 2019 [Member]
Derivative [Line Items]
Volume	36,960
Electricity (In MWH) [Member] | April 2019 [Member]
Derivative [Line Items]
Volume	3,520
Electricity (In MWH) [Member] | May 2019 [Member]
Derivative [Line Items]
Volume	3,520
Electricity (In MWH) [Member] | June 2019 [Member]
Derivative [Line Items]
Volume	3,200
Electricity (In MWH) [Member] | July 2019 [Member]
Derivative [Line Items]
Volume	7,040
Electricity (In MWH) [Member] | August 2019 [Member]
Derivative [Line Items]
Volume	7,040
Electricity (In MWH) [Member] | September 2019 [Member]
Derivative [Line Items]
Volume	3,200
Electricity (In MWH) [Member] | October 2019 [Member]
Derivative [Line Items]
Volume	3,680
Electricity (In MWH) [Member] | November 2019 [Member]
Derivative [Line Items]
Volume	3,200
Electricity (In MWH) [Member] | December 2019 [Member]
Derivative [Line Items]
Volume	3,360
Electricity (In MWH) [Member] | Calendar 2020 [Member]
Derivative [Line Items]
Volume	-
Electricity (In MWH) [Member] | Calendar 2021 [Member]
Derivative [Line Items]
Volume	-
Gas (in Dth) [Member] | October 2018 [Member]
Derivative [Line Items]
Volume	-
Gas (in Dth) [Member] | November 2018 [Member]
Derivative [Line Items]
Volume	538,650
Gas (in Dth) [Member] | December 2018 [Member]
Derivative [Line Items]
Volume	554,600
Gas (in Dth) [Member] | January 2019 [Member]
Derivative [Line Items]
Volume	812,530
Gas (in Dth) [Member] | February 2019 [Member]
Derivative [Line Items]
Volume	694,825
Gas (in Dth) [Member] | March 2019 [Member]
Derivative [Line Items]
Volume	627,875
Gas (in Dth) [Member] | April 2019 [Member]
Derivative [Line Items]
Volume	36,175
Gas (in Dth) [Member] | May 2019 [Member]
Derivative [Line Items]
Volume	30,450
Gas (in Dth) [Member] | June 2019 [Member]
Derivative [Line Items]
Volume	24,975
Gas (in Dth) [Member] | July 2019 [Member]
Derivative [Line Items]
Volume	20,100
Gas (in Dth) [Member] | August 2019 [Member]
Derivative [Line Items]
Volume	18,200
Gas (in Dth) [Member] | September 2019 [Member]
Derivative [Line Items]
Volume	17,750
Gas (in Dth) [Member] | October 2019 [Member]
Derivative [Line Items]
Volume	16,900
Gas (in Dth) [Member] | November 2019 [Member]
Derivative [Line Items]
Volume	18,575
Gas (in Dth) [Member] | December 2019 [Member]
Derivative [Line Items]
Volume	18,625
Gas (in Dth) [Member] | Calendar 2020 [Member]
Derivative [Line Items]
Volume	112,375
Gas (in Dth) [Member] | Calendar 2021 [Member]
Derivative [Line Items]
Volume	19,850

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

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