Share-Based Compensation Stock options (Detail) (Stock Options [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of unvested options at end of period	0
Unvested stock options decrease in period (in shares)	29,398
Stock option transactions under the terms of the LTSIP - shares [Roll Forward]
Balance at December 31, 2012	770,923
Granted	0
Exercised	(53,083)
Forfeited	0
Balance at December 31, 2013	717,840
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]
Balance at December 31, 2012	$ 11.35
Exercised	$ 4.75
Balance at December 31, 2013	$ 11.84
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Number of outstanding options at end of period (in shares)		717,840
Weighted-average remaining term (in years and months)	2 years 2 months
Weighted-average exercise price (in dollars per share)	$ 11.84
Number of exercisable options at end of period (in shares)	717,840
Weighted-average exercise price, options exercisable (in dollars per share)	$ 11.84
Stock options, additional disclosures [Abstract]
Aggregate intrinsic value of outstanding options (in shares)	$ 8.0
Aggregate intrinsic value of exercisable options	$ 8.0
Number of Questar stock options held by certain officers, employees and nonemployee directors of QEP (in shares)	298,098
Weighted-average exercise price of Questar stock options awarded to certain officers, employees and nonemployee directors of QEP (in dollars per share)	$ 11.41
Weighted-average remaining life of Questar stock options held by certain officers, employees and nonemployee directors of QEP (in years)	2 years 5 months
Options Outstanding Exercise Price Range 1 [Member]
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Minimum exercise price of options outstanding (in dollars per share)	$ 7.84
Maximum exercise price of options outstanding (in dollars per share)	$ 11.40
Number of outstanding options at end of period (in shares)		404,174
Weighted-average remaining term (in years and months)	1 year 11 months
Weighted-average exercise price (in dollars per share)	$ 10.52
Number of exercisable options at end of period (in shares)	404,174
Weighted-average exercise price, options exercisable (in dollars per share)	$ 10.52
Options Outstanding Exercise Price Range 2 [Member]
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Minimum exercise price of options outstanding (in dollars per share)	$ 13.10
Maximum exercise price of options outstanding (in dollars per share)	$ 17.35
Number of outstanding options at end of period (in shares)		313,666
Weighted-average remaining term (in years and months)	2 years 6 months
Weighted-average exercise price (in dollars per share)	$ 13.54
Number of exercisable options at end of period (in shares)	313,666
Weighted-average exercise price, options exercisable (in dollars per share)	$ 13.54
Minimum [Member]
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]
Balance at December 31, 2012	$ 4.37
Exercised	$ 4.37
Balance at December 31, 2013	$ 7.84
Maximum [Member]
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]
Balance at December 31, 2012	$ 17.35
Exercised	$ 13.10
Balance at December 31, 2013	$ 17.35
Questar Gas [Member]
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Minimum exercise price of options outstanding (in dollars per share)	$ 11.40
Maximum exercise price of options outstanding (in dollars per share)	$ 13.10
Number of outstanding options at end of period (in shares)		17,000
Weighted-average remaining term (in years and months)	2 years 7 months
Weighted-average exercise price (in dollars per share)	$ 12.10
Number of exercisable options at end of period (in shares)	17,000
Weighted-average exercise price, options exercisable (in dollars per share)	$ 12.10
Questar Pipeline [Member]
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Minimum exercise price of options outstanding (in dollars per share)	$ 7.84
Maximum exercise price of options outstanding (in dollars per share)	$ 13.10
Number of outstanding options at end of period (in shares)		158,933
Weighted-average remaining term (in years and months)	1 year 7 months
Weighted-average exercise price (in dollars per share)	$ 9.36
Number of exercisable options at end of period (in shares)	158,933
Weighted-average exercise price, options exercisable (in dollars per share)	$ 9.36