Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Total principal amount of debt	$ 3,001.8	$ 3,211.8
Less unamortized discount	(4.3)	(4.9)
Total long-term debt outstanding	2,997.5	3,206.9
Proceeds from Issuance of Long-term Debt	0	1,450.0	0
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
Non-cash loss on early extinguishment of debt	0	0.6	0.7
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	480.0	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)	2.22%	2.08%
Amount outstanding	480.0	690.0
Letters of credit outstanding	3.8	4.1
QEP Midstream's Credit Facility [Member]
Debt Instrument [Line Items]
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)	2.22%	2.05%
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