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Risk Management Activities (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Limit of GCA Volumes	20.00%
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	$ 0	$ 0
Interest Rate Swap
Derivative [Line Items]
Derivative, Notional Amount	$ 500,000,000.0
Minimum
Derivative [Line Items]
Commodity Contract Length	5 years
Maximum
Derivative [Line Items]
Commodity Contract Length	10 years

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Commodity Contract Length

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Limit of GCA Volumes

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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-Name Accounting Standards Codification
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-SubTopic 25
-Section 50
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 50
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