Basis of Presentation of Interim Consolidated Financial Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011		Jun. 30, 2012	Jun. 30, 2011
De-designation of commodity derivative contracts [Abstract]
Unrealized gain (Loss) on derivatives contract	$ (38.4)			$ 89.9	$ 58.8
REVENUES
Natural gas sales	138.9	298.7		300.1	611.3
Oil sales	107.2	80.7		218.0	143.7
NGL sales	82.1	63.8		179.5	111.7
Gathering, processing and other	45.8	58.9		95.6	105.5
OPERATING EXPENSES
Natural gas, oil and NGL transportation and other handling costs	40.7	24.0		75.2	45.7
Proved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets	48.9			49.3
Unproved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets	6.1			12.1
Southern Region [Member] | Proved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets	48.9
Southern Region [Member] | Unproved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets	3.1			6.1
Northern Region [Member] | Proved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets				0.4
Northern Region [Member] | Unproved Properties [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment of long-lived assets	3.0			6.0
QEP Field Services [Member]
REVENUES
NGL sales		16.5			33.7
Gathering, processing and other		123.5			221.4
Prior periods presentation of revenues [Member]
REVENUES
Natural gas sales		258.1	[1]		529.1	[1]
Oil sales		80.0	[1]		142.3	[1]
NGL sales		61.6	[1]		107.4	[1]
Gathering, processing and other		78.4	[1]		147.7	[1]
OPERATING EXPENSES
Natural gas, oil and NGL transportation and other handling costs		0	[1]		0	[1]
Prior periods presentation of revenues [Member] | QEP Field Services [Member]
REVENUES
NGL sales		45.1			73.7
Restatement Adjustment [Member]
REVENUES
Natural gas sales		40.6			82.2
Oil sales		0.7			1.4
NGL sales		2.2			4.3
Gathering, processing and other		(19.5)			(42.2)
OPERATING EXPENSES
Natural gas, oil and NGL transportation and other handling costs		$ 24.0			$ 45.7

[1] The "As reported" numbers reflect QEP Field Services NGL sales of $45.1 million and $73.7 million in the three and six months ended June 30, 2011, which have been reclassified from "Gathering, processing and other" into "NGL sales" for consistency with current period presentation. In its second quarter 2011 Form 10-Q, QEP reported "NGL sales" of $16.5 million and $33.7 million, and "Gathering, processing and other" of $123.5 million, and $221.4 million for the three and six months ended June 30, 2011, respectively. The QEP Field Services NGL reclassification is all within "Revenues" and has no effect on income from continuing operations, net income or earnings per share.