Share-Based Compensation Restricted shares (Details) (USD $)	12 Months Ended
Dec. 31, 2011
ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosures [Roll Forward]
Vesting period for share-based awards (in months)	6 months
Restricted Shares [Member]
Restricted share transactions under the terms of the LTSIP [Roll Forward]
Unvested restricted shares, beginning balance (recast) (in shares)	568,707
Granted (in shares)	348,127
Distributed (in shares)	(133,391)
Forfeited (in shares)	(11,893)
Unvested restricted shares, ending balance (in shares)	771,550
ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosures [Roll Forward]
Minimum price of unvested restricted shares, beginning of period (in dollars per share)	11.40
Maximum price of unvested restricted shares, beginning of the period (in dollars per share)	20.31
Minimum price of unvested restricted shares, granted (in dollars per share)	17.50
Maximum price of unvested restricted shares, granted (in dollars per share)	17.97
Minimum price of unvested restricted shares, distributed (in dollars per share)	11.40
Maximum price of unvested restricted shares, distributed (in dollars per share)	20.31
Minimum price of unvested restricted shares, forfeited (in dollars per share)	11.40
Maximum price of unvested restricted shares, forfeited (in dollars per share)	17.97
Minimum price of unvested restricted shares, end of period (in dollars per share)	11.40
Maximum price of unvested restricted shares, end of period (in dollars per share)	17.97
Weighted-average price, beginning of period (in dollars per share)	14.66
Weighted-average price, restricted shares granted (in dollars per share)	17.96
Weighted-average price, restricted shares distributed (in dollars per share)	14.09
Weighted-average price, restricted shares forfeited (in dollars per share)	16.45
Weighted-average price, end of period (in dollars per share)	16.22
Vesting period for share-based awards (in months)	14 months
Restricted share grants, vesting rights	Restricted share grants vest in equal installments over a three or four year period from the grant date
Questar Pipeline [Member]
Restricted share transactions under the terms of the LTSIP [Roll Forward]
Unvested restricted shares, ending balance (in shares)	153,888
ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosures [Roll Forward]
Minimum price of unvested restricted shares, end of period (in dollars per share)	11.40
Maximum price of unvested restricted shares, end of period (in dollars per share)	17.97
Weighted-average price, end of period (in dollars per share)	16.18
Vesting period for share-based awards (in months)	13 months
Questar Gas [Member]
Restricted share transactions under the terms of the LTSIP [Roll Forward]
Unvested restricted shares, ending balance (in shares)	89,561
ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosures [Roll Forward]
Minimum price of unvested restricted shares, end of period (in dollars per share)	11.40
Maximum price of unvested restricted shares, end of period (in dollars per share)	17.97
Weighted-average price, end of period (in dollars per share)	16.40
Vesting period for share-based awards (in months)	14 months

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The maximum price within a price range of unvested restricted shares.

+ References

No definition available.

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- Definition

The minimum price within a price range of unvested restricted shares.

+ References

No definition available.

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- Definition

The maximum price at which unvested restricted shares are forfeited under the plan

+ References

No definition available.

+ Details

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- Definition

The minimum price at which unvested restricted shares are forfeited under the plan

+ References

No definition available.

+ Details

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- Definition

The maximum price at which granted unvested restricted shares are converted into shares under the plan

+ References

No definition available.

+ Details

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- Definition

The minimum price at which granted unvested restricted shares are converted into shares under the plan

+ References

No definition available.

+ Details

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The maximum price at which unvested restricted shares are converted into shares and distributed under the plan

+ References

No definition available.

+ Details

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The minimum price at which unvested restricted shares are converted into shares and distributed under the plan

+ References

No definition available.

+ Details

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- Definition

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

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- Definition

Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

+ References

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-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

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- Definition

The number of shares under a share-based award plan other than a stock option plan that were settled during the reporting period due to a failure to satisfy vesting conditions pertaining to all option plans.

+ References

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-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(e)

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- Definition

The weighted average fair value as of the grant date of share-based award plans other than stock option plans that were not exercised or put into effect during the reporting period as a result of the occurrence of a terminating event specified in the contractual agreement of the plan.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(e)

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- Definition

The number of shares issuable under a share-based award plan pertaining to grants made during the period on other than stock option plans (for example, phantom stock plan, stock appreciation rights plan, performance target plan).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(c)

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- Definition

The weighted average fair value at grant for nonvested share-based awards issued during the period on other than stock option plans (for example, phantom stock plan, stock appreciation rights plan, performance target plan).

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(c)

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-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(1)

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- Definition

The number of outstanding awards on nonstock option plans (for example, phantom stock plan, stock appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

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- Definition

The weighted average fair value of nonvested awards on share-based plans excluding option plans (for example, phantom stock plan, stock appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

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- Definition

The decrease in the number of shares potentially issuable under a share-based award plan pertaining to awards for which the grantee has gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares, other instruments, or cash in accordance with the terms of the arrangement.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(d)

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- Definition

The weighted average fair value as of grant dates pertaining to a share-based award plan other than a stock option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares, other instruments, or cash in accordance with the terms of the arrangement.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(d)

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