Debt (Narrative) (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended	6 Months Ended
	Aug. 14, 2013	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 3,914.8	$ 3,914.8		$ 3,001.8
Revolving credit facility origination fees	(3.0)		(1.1)
Less unamortized discount		(4.0)	(4.0)		(4.3)
Debt Maturity Period		5 years 0 months 0 days
Proceeds from Issuance of Long-term Debt			300.0	0
Principal amount of senior notes outstanding		2,221.8	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]
Long-term Debt, Gross		1,093.0	1,093.0		480.0
Maturity date of long-term debt			Aug. 25, 2016
Borrowing capacity		1,500.0	1,500.0
Potential increased borrowing capacity		2,000.0	2,000.0
NumberOfMaturityDateExtensions		2	2
Additional period with in which maturity to be extended			1 year
Weighted-average interest rate (in hundredths)		2.20%	2.20%	2.33%
Amount outstanding		1,093.0	1,093.0
Letters of credit outstanding		3.8	3.8
QEP Midstream's Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		0	0		0
Maturity date of long-term debt			Aug. 14, 2018
Borrowing capacity		500.0	500.0
Potential increased borrowing capacity		750.0	750.0
Term Loan due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		600.0	600.0		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%	2.23%
6.05% Senior Notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		176.8	176.8		176.8
Long-term debt, interest rate (in hundredths)		6.05%	6.05%
Maturity date of long-term debt			Sep. 01, 2016
6.80% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 134.0	$ 134.0		$ 134.0
Long-term debt, interest rate (in hundredths)		6.80%	6.80%
Maturity date of long-term debt			Apr. 01, 2018