Acquisitions (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Acquisitions [Abstract]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual									$ 63.7
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual									14.9
Business Acquisition, Cost of Acquired Entity, Transaction Costs	1.1								1.1
Business Combination, Consideration Given [Abstract]
Cash Paid at Closing	1,388.7								1,388.7
Total estimate consideration given	1,388.7								1,388.7
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net [Abstract]
Proved properties	713.8								713.8
Unproved Properties	679.4								679.4
Asset retirement obligations	(0.9)								(0.9)
Liabilities assumed	(4.4)								(4.4)
Other assets	0.8								0.8
Business Acquisition, Pro Forma Information [Abstract]
Revenues	704.9	542.4	499.3	603.2	853.3	879.9	808.1	617.9	2,349.8	3,159.2	2,300.6
Pro Forma Revenues									2,485.3	3,236.7
NET INCOME ATTRIBUTABLE TO QEP	(23.1)	(3.1)	(0.7)	155.2	(0.3)	101.5	92.8	73.2	128.3	267.2	326.2
Pro Forma Net Income									$ 143.0	$ 259.8
Actual Basic total	$ (0.13)	$ (0.02)	$ 0.00	$ 0.87	$ (0.01)	$ 0.58	$ 0.52	$ 0.42	$ 0.72	$ 1.51	$ 1.86
Pro Forma Earnings Per Share, Basic									$ 0.80	$ 1.47
Actual Diluted total	$ (0.13)	$ (0.02)	$ 0.00	$ 0.87	$ 0.00	$ 0.57	$ 0.52	$ 0.41	$ 0.72	$ 1.50	$ 1.84
Pro Forma Earnings Per Share, Diluted									$ 0.80	$ 1.46