Risk Management and Derivatives: Utilities (Details) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2020 USD ($) MMBTU mW	Dec. 31, 2019 MMBTU mW
Derivative [Line Items]
Credit Risk Derivative Liabilities, at Fair Value \| $	$ 500
Natural Gas, Distribution \| Cash Flow Hedging
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	1,776,900
Natural Gas, Distribution \| Natural gas futures purchased
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	660,000	1,450,000
Derivative, Remaining Maturity	9 months	12 months
Natural Gas, Distribution \| Natural gas options purchased, net
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	950,000	3,240,000
Derivative, Remaining Maturity	9 months	3 months
Natural Gas, Distribution \| Natural gas basis swaps purchased
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	520,000	1,290,000
Derivative, Remaining Maturity	6 months	12 months
Natural Gas, Distribution \| Natural gas over-the-counter swaps, net
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	6,480,000	4,600,000
Derivative, Remaining Maturity	23 months	24 months
Natural Gas, Distribution \| Natural gas physical contracts, net
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount	8,085,376	13,548,235
Derivative, Remaining Maturity	9 months	12 months
Electricity \| Electric wholesale contracts
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| mW	141,225	0
Derivative, Remaining Maturity	6 months	0 months

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959

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Nominal number of units 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

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-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

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Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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