Price-per-share of common stock issued by the company.

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- Definition

The ratio used to modify the exercise price of options and the grant-day prices of restricted shares, to generally preserve the potential benefits under the LTSIP prior to the Spinoff.

+ References

No definition available.

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- Definition

The ratio used to modify the exercise price of options and the grant-day prices of restricted shares, to generally preserve the potential benefits under the LTSIP prior to the Spinoff.

+ References

No definition available.

+ Details

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- Definition

The estimated maximum dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

No definition available.

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- Definition

The estimated minimum dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

No definition available.

+ Details

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- Definition

The maximum period of time a share-based award is expected to be outstanding. A share-based award's expected term shall be determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior. An entity is required to aggregate individual awards into relatively homogeneous groups.

+ References

No definition available.

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- Definition

The minimum period of time a share-based award is expected to be outstanding. A share-based award's expected term shall be determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior. An entity is required to aggregate individual awards into relatively homogeneous groups.

+ References

No definition available.

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- Definition

The estimated maximum measure of the minimum percentage amount by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

+ Details

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- Definition

The estimated measure of the minimum percentage amount by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

No definition available.

+ Details

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

+ Details

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

No definition available.

+ Details

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- Definition

The maximum weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

No definition available.

+ Details

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- Definition

The minimum weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

No definition available.

+ Details

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

+ References

No definition available.

+ Details

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- Definition

Reductions in the entity's income taxes that arise when compensation cost (from non-qualified share-based compensation) recognized on the entity's tax return exceeds compensation cost from share-based compensation recognized in financial statements. This element represents the cash inflow reported in the enterprise's financing activities.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph i

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 00-15

-Paragraph 3

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock options, amortization of restricted stock, and adjustment for officers compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph e(2)(c)

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- Definition

The period of time a share-based award is expected to be outstanding. A share-based award's expected term shall be determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior. An entity is required to aggregate individual awards into relatively homogeneous groups.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph e(2)(a)

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section D

-Subsection 2

+ Details

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- Definition

The estimated measure of the percentage amount by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph e(2)(b)

+ Details

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own 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 e(2)(d)

+ Details

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- Definition

The difference between the maximum number of shares authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares already issued upon exercise of options or other share-based awards under the plan, and 2) shares reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

No definition available.

+ Details

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Data Type:	xbrli:sharesItemType
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Period Type:	instant

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph c(1)

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- Definition

Price-per-share of common or preferred stock issued or sold by the subsidiary or equity method investee.

+ References

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section H

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Share-Based Compensation Stock Options (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010 Years	Dec. 31, 2009 Years	Jun. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing price of Questar stock (in dollars per share)				$ 14.66
Ratio used to modify the exercise price and the grant-day prices of stock options and restricted share awards, Questar (in hundredths)				32.23%
Closing price of QEP stock (in dollars per share)				$ 30.83
Ratio used to modify the exercise price and the grant-day prices of stock options and restricted share awards, QEP (in hundredths)				67.77%
Share-based compensation	$ 10.1	$ 15.4	$ 9.3
Deferred share-based compensation on restricted share awards	3.6	6.3
Cash flow from income tax benefits in excess of recognized compensation expense	9.2	8.4	3.6
Shares available for future grant (in shares)	7,580,245
Major assumptions used in the calculation of fair value of options granted [Abstract]
Fair value of options at grant date (in dollars per share)		$ 13.10
Fair value of options at grant date - minimum range (in dollars per share)			$ 10.01
Fair value of options at grant date - maximum range (in dollars per share)			$ 11.40
Risk-free interest rate (in hundredths)		2.30%
Risk-free interest rate - minimum range (in hundredths)			1.78%
Risk-free interest rate - maximum range (in hundredths)			2.51%
Expected price volatility (in hundredths)		30.30%
Expected price volatility - minimum range (in hundredths)			28.10%
Expected price volatility - maximum range (in hundredths)			29.90%
Expected dividend yield (in hundredths)		1.18%
Expected dividend yield - minimum range (in hundredths)			1.39%
Expected dividend yield - maximum range (in hundredths)			1.61%
Expected life (in years)		5.2
Expected life - minimum range (in years)			5.0
Expected life - maximum range (in years)			5.0
Questar Pipeline [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	1.8	1.3	1.1
Questar Gas [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 1.1	$ 1.4	$ 1.0