Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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- Definition

Date Through Which Reclassifications Into Earnings From AOCI Will Take Place

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Life of Long-Term Debt Associated with Cash Flow Hedges (in years)

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- Definition

The time period estimated for the anticipated transfer of gains (losses), net from accumulated other comprehensive income into earnings.

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No definition available.

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- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

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- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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- Definition

Average fixed interest rate related to the group of interest rate derivatives.

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No definition available.

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- Definition

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

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-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (a),(c),(d),(e)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

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

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Derivatives and Hedging (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended		3 Months Ended
	Dec. 31, 2011	Dec. 31, 2014	Dec. 31, 2011	Mar. 31, 2012	Dec. 31, 2013	Jun. 30, 2011
Derivative [Line Items]
Derivative assets or liabilities outstanding		$ 0			$ 0
Cash Flow Hedging [Member] \| Questar Pipeline [Member] \| Forward Starting Interest Rate Swaps Terminated Q4 2011 [Member]
Derivative [Line Items]
Notional amount	150.0		150.0
Debt instrument, face amount	180.0		180.0
Derivative, loss on derivative	37.3
Life of long-term debt associated with cash flow hedges			30 years
Date through which reclassifications into earnings from AOCI will take place		2041
Pre-tax net losses expected to be reclassified from AOCI to earnings		0.6
Reclassification from accumulated OCI to income, estimated time to transfer		12 months
Fair Value Hedging [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount						125.0
Weighted-average fixed interest rate (in hundredths)						2.75%
Derivative, gain on derivative				$ 7.2