Derivative Contracts - Gain (Loss) in Statement of Financial Performance (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) derivative contracts not designated as hedging instruments	$ (35.4)	$ 50.7
Unrealized gain (loss) derivative contracts not designated as hedging instruments	(45.5)	(85.3)
Total gain (loss) on commodity derivative instruments	(80.9)	(34.6)
Natural gas derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(20.4)	44.6
Unrealized gain (loss) on commodity derivative contracts	(24.3)	(64.3)
Natural gas derivative contracts [Member] | QEP Marketing [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(1.4)	1.5
Unrealized gain (loss) on commodity derivative contracts	(0.3)	(1.7)
Oil derivative contracts [Member] | QEP Energy [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(12.9)	5.2
Unrealized gain (loss) on commodity derivative contracts	(20.9)	(19.7)
Interest Rate Swap [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(0.7)	(0.6)
Unrealized gain (loss) on commodity derivative contracts	0	0.4
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments	(0.7)	(0.2)
Realized and unrealized gains on commodity derivative instruments [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Realized gain (loss) on commodity derivative contracts	(34.7)	51.3
Unrealized gain (loss) on commodity derivative contracts	(45.5)	(85.7)
Total gain (loss) on commodity derivative instruments	$ (80.2)	$ (34.4)