Gain (Loss) in Statement of Financial Performance (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) derivative contracts not designated as hedging instruments	$ (35.3)	$ 30.1	$ (70.7)	$ 80.8
Unrealized gain (loss) derivative contracts not designated as hedging instruments	(52.7)	83.9	(98.2)	(1.4)
Total gain (loss) on commodity derivative instruments	(88.0)	114.0	(168.9)	79.4
Realized and unrealized gains on commodity derivative instruments [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(34.1)	30.8	(68.8)	82.1
Unrealized gain (loss) on commodity derivative contracts	(51.1)	79.4	(96.6)	(6.3)
Total gain (loss) on commodity derivative instruments	(85.2)	110.2	(165.4)	75.8
Natural gas derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(8.4)	24.9	(28.8)	69.5
Unrealized gain (loss) on commodity derivative contracts	6.0	61.3	(18.1)	(3.0)
Natural gas derivative contracts [Member] | QEP Marketing [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(0.6)	(0.5)	(2.0)	1.0
Unrealized gain (loss) on commodity derivative contracts	0.7	1.3	0.4	(0.4)
Oil derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(25.1)	6.4	(38.0)	11.6
Unrealized gain (loss) on commodity derivative contracts	(57.8)	16.8	(78.9)	(2.9)
Interest Rate Swap [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(1.2)	(0.7)	(1.9)	(1.3)
Unrealized gain (loss) on commodity derivative contracts	(1.6)	4.5	(1.6)	4.9
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments	$ (2.8)	$ 3.8	$ (3.5)	$ 3.6