Derivative Contracts - Gain (Loss) in Statement of Financial Performance (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Fair value of frozen derivative to be settled and reclassified within twelve months			$ 36.9
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) derivative contracts not designated as hedging instruments	30.1	120.7	80.8	208.7
Unrealized gain (loss) derivative contracts not designated as hedging instruments	83.9	(38.4)	(1.4)	89.9
Total gain (loss) on commodity derivative instruments			79.4	298.6
Natural gas derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	24.9	111.9	69.5	197.6
Unrealized gain (loss) on commodity derivative contracts	61.3	(78.4)	(3.0)	53.9
Natural gas derivative contracts [Member] | QEP Marketing [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(0.5)	0.6	1.0	4.1
Unrealized gain (loss) on commodity derivative contracts	1.3	(0.7)	(0.4)	0.9
Oil derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	6.4	2.2	11.6	(0.5)
Unrealized gain (loss) on commodity derivative contracts	16.8	38.6	(2.9)	27.1
NGL derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	0	2.7	0	3.1
Unrealized gain (loss) on commodity derivative contracts	0	4.9	0	7.8
NGL derivative contracts [Member] | QEP Field Services [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	0	3.3	0	4.4
Unrealized gain (loss) on commodity derivative contracts	0	1.5	0	4.5
Interest Rate Swap [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(0.7)	0	(1.3)	0
Unrealized gain (loss) on commodity derivative contracts	4.5	(4.3)	4.9	(4.3)
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments	3.8	(4.3)	3.6	(4.3)
Total gain (loss) on commodity derivative instruments	114.0	82.3
Realized and unrealized gains on commodity derivative instruments [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	30.8	120.7	82.1	208.7
Unrealized gain (loss) on commodity derivative contracts	79.4	(34.1)	(6.3)	94.2
Total gain (loss) on commodity derivative instruments	$ 110.2	$ 86.6	$ 75.8	$ 302.9