Debt Maturities of Long-term Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Debt Maturities [Line Items]
Number of years of long-term debt maturities	5 years
Maturities of Long-term Debt [Abstract]
2012	$ 91.5
2013	42.0
2014	0
2015	25.1
2016	250.0
Questar Corp [Member]
Maturities of Long-term Debt [Abstract]
2012	0
2013	0
2014	0
2015	0
2016	250.0
Questar Pipeline [Member]
Maturities of Long-term Debt [Abstract]
2012	0
2013	0
2014	0
2015	25.1
2016	0
Questar Gas [Member]
Maturities of Long-term Debt [Abstract]
2012	91.5
2013	42.0
2014	0
2015	0
2016	$ 0

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This is the number of years that are being disclosed for long-term debt maturities beginning with the current year.

+ References

No definition available.

+ Details

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- Definition

Amount of long-term debt maturing within the next twelve months following the date of the latest balance sheet presented in the financial statements, which may include maturities of long-term debt, sinking fund requirements, and other securities redeemable at fixed or determinable prices and dates.

+ References