CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Balance at Dec. 31, 2012	$ 3,313.7	$ 1.8	$ (3.7)	$ 462.1	$ 2,773.0	$ 32.8	$ 47.7
Shares, Issued at Dec. 31, 2012		178.5
Treasury Stock, Shares at Dec. 31, 2012			(0.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	159.4				159.4		12.0
Total net income including portion attributable to noncontrolling interest	171.4
Dividends	(14.3)				(14.3)
Equity-based compensation	25.0		$ (11.2)	36.3	(0.3)		0.2
Equity-based compensation, shares issued		1.2
Equity-based compensation, treasury shares reissued			(0.3)
Distribution of noncontrolling interest	(9.3)						(9.3)
Net proceeds from QEP Midstream initial public offering	449.6						449.6
Reclassification of previously deferred derivative gains in OCI, net of tax	(77.6)					(77.6)
Change in pension and postretirement liability, net of tax	18.3					18.3
Balance at Dec. 31, 2013	3,876.8	$ 1.8	$ (14.9)	498.4	2,917.8	(26.5)	500.2
Treasury Stock, Shares at Dec. 31, 2013			(0.4)
Shares, Issued at Dec. 31, 2013		179.7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	784.4				784.4
Total net income including portion attributable to noncontrolling interest	784.4
Dividends	(14.6)				(14.6)
Equity-based compensation	26.6		$ (10.5)	36.9			0.2
Equity-based compensation, shares issued		1.2
Equity-based compensation, treasury shares reissued			(0.4)
Distribution of noncontrolling interest	(31.9)						(31.9)
Net proceeds from QEP Midstream initial public offering	0.0
Common stock repurchased and retired	99.7				99.7
Common stock repurchased and retired, shares		4.7
Change in pension and postretirement liability, net of tax	2.2					2.2
Noncontrolling interest decrease from Midstream Sale	(468.5)						(468.5)
Balance at Dec. 31, 2014	$ 4,075.3	$ 1.8	$ (25.4)	535.3	3,587.9	(24.3)	0.0
Treasury Stock, Shares at Dec. 31, 2014	(0.8)		(0.8)
Shares, Issued at Dec. 31, 2014		176.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (149.4)				(149.4)
Total net income including portion attributable to noncontrolling interest	(149.4)
Dividends	(14.1)				(14.1)
Equity-based compensation	24.2		$ 10.8	19.5	(6.1)
Equity-based compensation, shares issued		1.1
Equity-based compensation, treasury shares reissued			0.3
Net proceeds from QEP Midstream initial public offering	0.0
Change in pension and postretirement liability, net of tax	11.9					11.9
Balance at Dec. 31, 2015	$ 3,947.9	$ 1.8	$ (14.6)	$ 554.8	$ 3,418.3	$ (12.4)	$ 0.0
Treasury Stock, Shares at Dec. 31, 2015	(0.5)		(0.5)
Shares, Issued at Dec. 31, 2015		177.3