Debt (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Debt Instrument [Line Items]
Total principal amount of debt	$ 2,886.8	$ 3,211.8
Less unamortized discount	(4.5)	(4.9)
Total long-term debt outstanding	2,882.3	3,206.9
Principal amount of senior notes outstanding	2,221.8
Debt Instrument, Maturity Date Range, Start	Sep. 01, 2016
Debt Instrument, Maturity Date Range, End	May 01, 2023
Senior Notes, stated interest rate, minimum (in hundredths)	5.25%
Senior Notes, stated interest rate, maximim (in hundredths)	6.875%
Revolving Credit Facility due 2016 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	365.0	690.0
Maturity date of long-term debt	Aug. 25, 2016
Borrowing capacity	1,500.0
Potential increased borrowing capacity	2,000.0
Number of maturity date extentions	2
Additional period with in which maturity to be extended	1 year
Weighted-average interest rate (in hundredths)	2.56%		2.05%
Amount outstanding	365.0
Letters of credit outstanding	3.7
QEP Midstream's Credit Facility [Member]
Debt Instrument [Line Items]
Total principal amount of debt	0	0
Maturity date of long-term debt	Aug. 14, 2018
Borrowing capacity	500.0
Potential increased borrowing capacity	750.0
Term Loan due 2017 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	300.0	300.0
Maturity date of long-term debt	Apr. 18, 2017
Additional period with in which maturity to be extended	1 year
Weighted-average interest rate (in hundredths)	2.23%		2.02%
6.05% Senior Notes due 2016 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	176.8	176.8
Long-term debt, interest rate (in hundredths)	6.05%
Maturity date of long-term debt	Sep. 01, 2016
Maturity period of long-term debt	5 years
6.80% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	134.0	134.0
Long-term debt, interest rate (in hundredths)	6.80%
Maturity date of long-term debt	Apr. 01, 2018
6.80% Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	136.0	136.0
6.875% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	625.0	625.0
5.375% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	500.0	500.0
5.25% Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Total principal amount of debt	$ 650.0	$ 650.0