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Long-term debt Issued (Details 2) - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 13, 2019	Jun. 07, 2019	Apr. 04, 2019	Dec. 31, 2018	Apr. 25, 2017
Long-term debt issued [Line Items]
Long-term debt	$ 2,379,806				$ 2,108,695
Senior Notes
Long-term debt issued [Line Items]
Long-term debt	$ 1,656,000				1,381,000
Weighted Average Interest Rate	4.52%
Credit Agreements
Long-term debt issued [Line Items]
Long-term debt	$ 11,075				$ 110,100
Weighted Average Interest Rate	5.50%
Centennial Energy Holdings, Inc. [Member] | Senior Notes
Long-term debt issued [Line Items]
Long-term debt				$ 150,000
Weighted Average Interest Rate				4.60%
Cascade Natural Gas [Member] | Senior Notes
Long-term debt issued [Line Items]
Long-term debt		$ 75,000
Weighted Average Interest Rate		3.93%
Cascade Natural Gas [Member] | Credit Agreements
Long-term debt issued [Line Items]
Long-term debt			$ 100,000			$ 75,000
Intermountain Gas Company [Member] | Senior Notes
Long-term debt issued [Line Items]
Long-term debt		$ 50,000
Weighted Average Interest Rate		3.92%

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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-Publisher FASB
-Name Accounting Standards Codification
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Weighted average interest rate of long-term debt outstanding calculated at point in time.

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