Derivative Contracts Gain (Loss) in Statement of Financial Performance (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Realized gain (loss) derivative contracts not designated as hedging instruments	$ 104.4	$ (35.4)
Unrealized gain (loss) derivative contracts not designated as hedging instruments	(23.5)	(45.5)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	80.9	(80.9)
Realized and unrealized gains on commodity derivative instruments [Member]
Derivative [Line Items]
Realized gain (loss) on commodity derivative contracts not designated as hedging instruments	104.4	(34.7)
Unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments	(23.5)	(45.5)
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments	80.9	(80.2)
Natural gas derivative contracts [Member] \| Realized and unrealized gains on commodity derivative instruments [Member] \| QEP Energy [Member]
Derivative [Line Items]
Realized gain (loss) on commodity derivative contracts not designated as hedging instruments	17.9	(20.4)
Unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments	11.4	(24.3)
Natural gas derivative contracts [Member] \| Realized and unrealized gains on commodity derivative instruments [Member] \| QEP Marketing [Member]
Derivative [Line Items]
Realized gain (loss) on commodity derivative contracts not designated as hedging instruments	2.5	(1.4)
Unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments	(1.8)	(0.3)
Oil derivative contracts [Member] \| Realized and unrealized gains on commodity derivative instruments [Member] \| QEP Energy [Member]
Derivative [Line Items]
Realized gain (loss) on commodity derivative contracts not designated as hedging instruments	84.0	(12.9)
Unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments	(33.1)	(20.9)
Interest Rate Swap [Member] \| Realized And Unrealized Gains Losses On Interest Rate Swaps [Member]
Derivative [Line Items]
Realized gain (loss) on commodity derivative contracts not designated as hedging instruments	0	(0.7)
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments	$ 0	$ (0.7)

Total Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments

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- Definition

Realized gain (loss) derivative contracts not designated as hedging instruments

+ References

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- Definition

Represents the realized gain (loss) on commodity derivative contracts not designated as hedging instruments for the period.

+ References

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- Definition

Unrealized gain (loss) derivative contracts not designated as hedging instruments

+ References

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- Definition

Represents the unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments for the period.

+ References

No definition available.

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- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

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