Derivative Contracts (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Forecasted production from proved reserves (in hundredths)	100.00%
Unrealized gains on derivative contracts	$ 182.9
Unrealized gains on derivative contracts, net of tax	114.9
Notional amount of interest rate derivatives	300.0
Derivatives, Fair Value [Line Items]
Total principal amount of debt	3,185.8		1,684.9
Derivative Contracts - Volumes and Prices
Notional amount of interest rate derivatives	300.0
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	237.6		407.6
Derivative Liability, Fair Value, Gross	22.0		11.7
Commodity Contract [Member] | Short-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	199.4		284.1
Derivative Liability, Fair Value, Gross	12.3		11.7
Commodity Contract [Member] | Long-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	38.2		123.5
Derivative Liability, Fair Value, Gross	3.0		0
Commodity Contract [Member] | Oil Sales (Bbls) [Member] | 2012 [Member] | NYMEX WTI [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	NYMEX WTI
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	400,000
Collars Floor Price ($ per unit)	87.50
Collars Ceiling Price ($ per unit)	115.36
Interest Rate Swap [Member] | Short-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	0		0
Derivative Liability, Fair Value, Gross	2.6		0
Interest Rate Swap [Member] | Long-term [Member]
Fair Value of Derivative Contracts, Gross [Abstract]
Derivative Asset, Fair Value, Gross	0		0
Derivative Liability, Fair Value, Gross	4.1		0
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2012 [Member] | NYMEX [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	NYMEX
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	19,300,000
Average Swap price per unit ($ per unit)	4.72
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2012 [Member] | IFPEPL [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	IFPEPL (1)	[1]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	1,800,000
Average Swap price per unit ($ per unit)	4.70
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2012 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	IFNPCR (2)	[2]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	22,100,000
Average Swap price per unit ($ per unit)	4.67
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2012 [Member] | IFCNPTE [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	IFCNPTE (3)	[3]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	2,800,000
Average Swap price per unit ($ per unit)	2.66
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2013 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year	2013
Index	IFNPCR (2)	[2]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	65,700,000
Average Swap price per unit ($ per unit)	5.66
Swap [Member] | Natural Gas Sales (MMbtu) [Member] | 2013 [Member] | NYMEX WTI [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)	29,200,000
Average Swap price per unit ($ per unit)	3.68
Swap [Member] | Oil Sales (Bbls) [Member] | 2012 [Member] | NYMEX WTI [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	NYMEX WTI
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	1,300,000
Average Swap price per unit ($ per unit)	97.42
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)	5,100,000
Average Swap price per unit ($ per unit)	98.48
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)	1,800,000
Average Swap price per unit ($ per unit)	92.72
Swap [Member] | NGL Sales [Member] | 2012 [Member] | Mt. Belvieu Ethane [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	Mt. Belvieu Ethane
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	3,900,000
Average Swap price per unit ($ per unit)	0.64
Swap [Member] | NGL Sales [Member] | 2012 [Member] | Mt. Belvieu Propane [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	Mt. Belvieu Propane
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	5,800,000
Average Swap price per unit ($ per unit)	1.28
Swap [Member] | QEP Field Services [Member] | 2012 [Member] | Mt. Belvieu Ethane [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	Mt. Belvieu Ethane
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	3,900,000
Average Swap price per unit ($ per unit)	0.64
Swap [Member] | QEP Field Services [Member] | 2012 [Member] | Mt. Belvieu Propane [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	Mt. Belvieu Propane
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	1,900,000
Average Swap price per unit ($ per unit)	1.28
Swap [Member] | QEP Marketing [Member] | 2012 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	IFNPCR (1)	[2]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	2,100,000
Average Swap price per unit ($ per unit)	3.93
Swap [Member] | QEP Marketing [Member] | 2013 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year	2013
Index	IFNPCR (1)	[2]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	3,100,000
Average Swap price per unit ($ per unit)	3.77
Swap [Member] | QEP Resources [Member]
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional amount of interest rate derivatives	300.0
Derivative Contracts - Volumes and Prices
Notional amount of interest rate derivatives	300.0
Maturity	Mar. 31, 2017
Fixed Rate Paid (in hundredths)	1.07%
Variable Rate Received	One month LIBOR
Swap [Member] | Purchased Gas and Oil Expense [Member] | 2012 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year	2012
Index	IFNPCR (1)	[2]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	1,500,000
Average Swap price per unit ($ per unit)	2.76
Swap [Member] | Purchased Gas and Oil Expense [Member] | 2013 [Member] | IFNPCR [Member]
Derivatives, Fair Value [Line Items]
Year	2013
Index	IFNPCR (1)	[2]
Derivative Contracts - Volumes and Prices
Total Volume (in Bcf, Mbbl, millions of gallons, millions of MMBtu)	100,000
Average Swap price per unit ($ per unit)	2.59
Term Loan due 2017 [Member]
Derivatives, Fair Value [Line Items]
Total principal amount of debt	$ 300.0		$ 0

[1] Inside FERC monthly settlement index for the Panhandle Eastern Pipeline Company.

[2] Inside FERC monthly settlement index for the Northwest Pipeline Corp. Rocky Mountains.

[3] Inside FERC monthly settlement index for Centerpoint East.