Share-Based Compensation Stock options (Details) (Stock Options [Member], USD $)	9 Months Ended
	Sep. 30, 2014
Stock option transactions under the terms of the LTSIP - shares [Roll Forward]
Balance at December 31, 2013	717,840
Granted	0
Exercised	(67,559)
Forfeited	0
Balance at September 30, 2014	650,281
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]
Balance at December 31, 2013	$ 11.84
Exercised	$ 8.78
Balance at September 30, 2014	$ 12.16
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Options Outstanding, Number outstanding at end of period (in shares)	650,281
Options Outstanding, Weighted-average remaining term (in years and months)	1 year 6 months
Options Outstanding, Weighted-average exercise price	$ 12.16
Options Exercisable, Number exercisable at end of period	650,281
Options Exercisable, Weighted-average exercise price	$ 12.16
Stock options, additional disclosures [Abstract]
Number of unvested options at end of period (in shares)	0
Number of Questar stock options held by certain officers, employees and nonemployee directors of QEP (in shares)	245,332
Weighted-average exercise price of Questar stock options awarded to certain officers, employees and nonemployee directors of QEP (in dollars per share)	$ 11.34
Weighted-average remaining life of Questar stock options held by certain officers, employees and nonemployee directors of QEP (in years)	1 year 8 months
$7.84 - $11.40 [Member]
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Range of exercise prices, lower limit	$ 7.84
Range of exercise prices, upper limit	$ 11.40
Options Outstanding, Number outstanding at end of period (in shares)	341,948
Options Outstanding, Weighted-average remaining term (in years and months)	1 year 3 months
Options Outstanding, Weighted-average exercise price	$ 10.90
Options Exercisable, Number exercisable at end of period	341,948
Options Exercisable, Weighted-average exercise price	$ 10.90
$13.10 - $17.35 [Member]
Stock options outstanding, exercisable and unvested at end of period, by exercise price range [Abstract]
Range of exercise prices, lower limit	$ 13.10
Range of exercise prices, upper limit	$ 17.35
Options Outstanding, Number outstanding at end of period (in shares)	308,333
Options Outstanding, Weighted-average remaining term (in years and months)	1 year 9 months
Options Outstanding, Weighted-average exercise price	$ 13.55
Options Exercisable, Number exercisable at end of period	308,333
Options Exercisable, Weighted-average exercise price	$ 13.55
Minimum [Member]
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]
Balance at December 31, 2013	$ 7.84
Exercised	$ 7.84
Balance at September 30, 2014	$ 7.84
Maximum [Member]
Stock option transactions under the terms of the LTSIP - exercise price [Roll Forward]
Balance at December 31, 2013	$ 17.35
Exercised	$ 13.10
Balance at September 30, 2014	$ 17.35