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Debt Short-term borrowings (Details 2) (Short-term debt [Member], Revolving credit agreement [Member], USD $) In Millions, unless otherwise specified | Dec. 31, 2012
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Cascade Natural Gas Corporation [Member] |
Short-term debt [Line Items] |
Short-term debt, weighted average interest rate | 3.30%
Ratio of total debt to total capitalization as specified in debt convenants. | 65.00%
Intermountain Gas Company [Member] |
Short-term debt [Line Items] |
Short-term debt, weighted average interest rate | 2.30%
Ratio of total debt to total capitalization as specified in debt convenants. | 65.00%
Conditions resulting in an early termination date under any swap contract that is in excess of this amount | 10.0

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- Definition Conditions resulting in an early termination date under any swap contract that is in excess of this amount + References No definition available. + Details
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- Definition Ratio of total debt to total capitalization as specified in debt convenants. + References No definition available. + Details
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- Details
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- Definition Reflects the calculation as of the balance sheet date of the average interest rate weighted by the amount of short-term debt outstanding by type or by instrument at that time. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph b -Article 5 + Details
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