Derivative Contracts - Gain (Loss) in Statement of Financial Performance (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) derivative contracts not designated as hedging instruments	$ 26.3	$ 93.2	$ 107.1	$ 301.9
Unrealized gain (loss) derivative contracts not designated as hedging instruments	(54.1)	(57.1)	(55.5)	32.8
Total gain (loss) on commodity derivative instruments			51.6	334.7
Natural gas derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	42.5	86.2	112.0	283.8
Unrealized gain (loss) on commodity derivative contracts	(6.6)	(50.6)	(9.6)	3.3
Natural gas derivative contracts [Member] | QEP Marketing [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(0.3)	(0.4)	0.7	3.7
Unrealized gain (loss) on commodity derivative contracts	0.1	(1.4)	(0.3)	(0.5)
Oil derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(15.3)	2.7	(3.7)	2.2
Unrealized gain (loss) on commodity derivative contracts	(46.2)	4.1	(49.1)	31.2
NGL derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	0	3.4	0	6.5
Unrealized gain (loss) on commodity derivative contracts	0	(4.4)	0	3.4
NGL derivative contracts [Member] | QEP Field Services [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	0	1.9	0	6.3
Unrealized gain (loss) on commodity derivative contracts	0	(2.5)	0	2.0
Interest Rate Swap [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(0.6)	(0.6)	(1.9)	(0.6)
Unrealized gain (loss) on commodity derivative contracts	(1.4)	(2.3)	3.5	(6.6)
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments	(2.0)	(2.9)	1.6	(7.2)
Total gain (loss) on commodity derivative instruments	(27.8)	36.1
Realized and unrealized gains on commodity derivative instruments [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	26.9	93.8	109.0	302.5
Unrealized gain (loss) on commodity derivative contracts	(52.7)	(54.8)	(59.0)	39.4
Total gain (loss) on commodity derivative instruments	$ (25.8)	$ 39.0	$ 50.0	$ 341.9