CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Net (loss) income	$ (2.1)		$ 102.4		$ 154.1		$ 269.7
Other comprehensive (loss) income, net of tax:
Reclassification of previously deferred derivative gains(1)	(42.1)	[1]	37.3	[1]	(133.8)	[1]	(13.0)	[1]
Pension and other postretirement plans adjustments:
Amortization of net actuarial loss	0.5	[2]	0	[2]	0.7	[2]	0	[2]
Amortization of prior service cost	0.9	[3]	1.4	[3]	2.6	[3]	3.1	[3]
Total pension and other postretirement plans adjustments	1.4		1.4		3.3		3.1
Other comprehensive loss	(40.7)		38.7		(130.5)		(9.9)
Comprehensive (loss) income	(42.8)		141.1		23.6		259.8
Comprehensive income attributable to noncontrolling interests	(1.0)		(0.9)		(2.7)		(2.2)
Comprehensive (loss) income attributable to QEP	$ (43.8)		$ 140.2		$ 20.9		$ 257.6

[1] Presented net of income tax benefit of $24.9 million and $79.2 million during the three and nine months ended September 30, 2012, respectively, and net of income tax expense of $22.1 million during the three months ended September 30, 2011 and income tax benefit of $7.7 million during the nine months ended September 30, 2011, respectively.

[2] Presented net of income tax expense of $0.2 million and $0.4 million during the three and nine months ended September 30, 2012, respectively.

[3] Presented net of income tax expense of $0.5 million and $1.6 million during three and nine months ended September 30, 2012, respectively, and net of income tax expense of $0.8 million and $1.9 million during the three and nine months ended September 30, 2011, respectively.