Derivative Contracts (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		Dec. 31, 2012
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Forecasted production from proved reserves (in hundredths)					100.00%
Unrealized gains on derivative contracts	$ 58.7				$ 58.7
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	36.9				36.9
Notional amount of interest rate derivatives	300.0				300.0
Derivatives, Fair Value [Line Items]
Total principal amount of debt	3,410.3				3,410.3				3,211.8
Derivative Contracts - Volumes and Prices
Notional amount of interest rate derivatives	300.0				300.0
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	124.7				124.7				193.9
Derivative Liability, Fair Value, Gross	4.2				4.2				7.3
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	(20.6)	[1]	(44.7)	[1]	(40.7)	[1]	(91.7)	[1]
Commodity Contract [Member] | Short-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	105.8				105.8				189.7
Derivative Liability, Fair Value, Gross	1.7				1.7				1.0
Commodity Contract [Member] | Long-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	17.6				17.6				4.2
Derivative Liability, Fair Value, Gross	0				0				0.1
Interest Rate Swap [Member] | Short-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	0				0				0
Derivative Liability, Fair Value, Gross	2.5				2.5				2.6
Interest Rate Swap [Member] | Long-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	1.3				1.3				0
Derivative Liability, Fair Value, Gross	0				0				3.6
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2013 [Member] | NYMEX [Member]
Derivatives, Fair Value [Line Items]
Year					2013
Index					NYMEX
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	29,400,000				29,400,000
Average Swap price per unit ($ per unit)	3.81				3.81
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2013 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year					2013
Index					IFNPCR (1)
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	36,800,000				36,800,000
Average Swap price per unit ($ per unit)	5.49				5.49
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2014 [Member] | NYMEX [Member]
Derivatives, Fair Value [Line Items]
Year					2014
Index					NYMEX
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	25,600,000				25,600,000
Average Swap price per unit ($ per unit)	4.19				4.19
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2014 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year					2014
Index					IFNPCR (1)
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	32,900,000				32,900,000
Average Swap price per unit ($ per unit)	4.00				4.00
Swap [Member] | Oil Sales (Bbls) [Member] | 2013 [Member] | NYMEX WTI [Member]
Derivatives, Fair Value [Line Items]
Year					2013
Index					NYMEX WTI
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	2,900,000				2,900,000
Average Swap price per unit ($ per unit)	98.33				98.33
Swap [Member] | Oil Sales (Bbls) [Member] | 2013 [Member] | BRENT ICE [Member]
Derivatives, Fair Value [Line Items]
Year					2013
Index					BRENT ICE
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	200,000				200,000
Average Swap price per unit ($ per unit)	107.80				107.80
Swap [Member] | Oil Sales (Bbls) [Member] | 2014 [Member] | NYMEX WTI [Member]
Derivatives, Fair Value [Line Items]
Year					2014
Index					NYMEX WTI
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	5,500,000				5,500,000
Average Swap price per unit ($ per unit)	92.59				92.59
Swap [Member] | QEP Marketing [Member] | 2013 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year					2013
Index					IFNPCR
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	1,600,000				1,600,000
Average Swap price per unit ($ per unit)	3.82				3.82
Swap [Member] | QEP Resources [Member]
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional amount of interest rate derivatives	300.0				300.0
Derivative Contracts - Volumes and Prices
Notional amount of interest rate derivatives	300.0				300.0
Maturity					Mar. 31, 2017
Fixed Rate Paid (in hundredths)	1.07%				1.07%
Variable Rate Received					One month LIBOR
Swap [Member] | Purchased Gas and Oil Expense [Member] | 2013 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year					2013
Index					IFNPCR
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	500,000				500,000
Average Swap price per unit ($ per unit)	3.83				3.83
Swap [Member] | Purchased Gas and Oil Expense [Member] | 2014 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year					2014
Index					IFNPCR
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	100,000				100,000
Average Swap price per unit ($ per unit)	3.87				3.87
Term Loan due 2017 [Member]
Derivatives, Fair Value [Line Items]
Total principal amount of debt	$ 300.0				$ 300.0				$ 300.0

[1] Presented net of income tax benefit of $12.2 million and $24.1 million during the three and six months ended June 30, 2013 and $26.5 million and $54.3 million during the three and six months ended June 30, 2012, respectively.