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Risk Management and Derivatives: Derivatives Not Designated as Hedge Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivative [Line Items]
Regulatory Liabilities	$ 526,417		$ 526,417		$ 532,720
Regulatory assets	(830,055)		(830,055)		(278,258)
Gas price derivatives
Derivative [Line Items]
Regulatory Liabilities	13,234		13,234		0
Gas price derivatives
Derivative [Line Items]
Regulatory assets	0		0		$ (2,226)
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	6,498	$ 391	3,558	$ 2,764
Not Designated as Hedging Instrument | Fuel, purchased power and cost of natural gas sold | Electricity
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	2,494	(1,386)	(2,628)	(228)
Not Designated as Hedging Instrument | Fuel, purchased power and cost of natural gas sold | Natural Gas, Distribution
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 4,004	$ 1,777	$ 6,186	$ 2,992

X

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
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