Basis of Presentation of Interim Consolidated Financial Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011		Sep. 30, 2012	Sep. 30, 2011
De-designation of commodity derivative contracts [Abstract]
Unrealized gain (Loss) on derivatives contract	$ (57.1)			$ 32.8	$ 86.7
REVENUES
Natural gas sales	170.3	309.8		470.4	921.1
Oil sales	117.7	76.9		335.7	220.6
NGL sales	67.5	79.3		247.0	191.0
Gathering, processing and other	46.3	57.1		141.9	162.6
OPERATING EXPENSES
Natural gas, oil and NGL transportation and other handling costs	36.3	27.5		111.5	73.2
QEP Field Services [Member]
REVENUES
NGL sales		34.1			67.8
Gathering, processing and other		118.7			340.1
Prior periods presentation of revenues [Member]
REVENUES
Natural gas sales		266.7	[1]		795.8	[1]
Oil sales		76.1	[1]		218.4	[1]
NGL sales		75.7	[1]		183.1	[1]
Gathering, processing and other		77.1	[1]		224.8	[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		41.6			115.3
Restatement Adjustment [Member]
REVENUES
Natural gas sales		43.1			125.3
Oil sales		0.8			2.2
NGL sales		3.6			7.9
Gathering, processing and other		(20.0)			(62.2)
OPERATING EXPENSES
Natural gas, oil and NGL transportation and other handling costs		$ 27.5			$ 73.2

[1] The “As reported” numbers reflect QEP Field Services NGL sales of $41.6 million and $115.3 million for the three and nine months ended September 30, 2011, which were reclassified from “Gathering, processing and other” into “NGL sales” for consistency with current period presentation. In its third quarter 2011 Form 10-Q, QEP reported “NGL sales” of $34.1 million and $67.8 million, and “Gathering, processing and other” of $118.7 million and $340.1 million for the three and nine months ended September 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.