CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock, Value [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Stockholders' Equity, Total [Member]
Balance at Dec. 31, 2013		$ 1.8	$ (14.9)	$ 498.4	$ 2,917.8	$ (26.5)	$ 500.2	$ 3,876.8
Shares at Dec. 31, 2013		179.7
Treasury shares at Dec. 31, 2013			(0.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (784.4)	$ 0.0	$ 0.0	0.0	784.4	0.0	0.0	784.4
Stockholders' Equity, Other Shares		0.0	0.0
Dividends		0.0	0.0
Dividends		$ 0.0	$ 0.0	0.0	(14.6)	0.0	0.0	(14.6)
Share-based compensation		$ 0.0	$ (10.5)	36.9	0.0	0.0	0.2	26.6
Share-based compensation, shares		1.2	(0.4)
Distribution of noncontrolling interest		$ 0.0	$ 0.0	0.0	0.0	0.0	(31.9)	(31.9)
Distribution of noncontrolling interest, shares		0.0	0.0
Common stock repurchased and retired		$ 0.0	$ 0.0	0.0	(99.7)	0.0	0.0	(99.7)
Common stock repurchased and retired, shares		(4.7)	0.0
Noncontrolling interest decrease from sale of substantially all of QEP's midstream business		$ 0.0	$ 0.0	0.0	0.0	0.0	(468.5)	(468.5)
Noncontrolling interest decrease from sale of substantially all of QEP's midstream business, shares		0.0	0.0
Change in pension and postretirement liability, net of tax, shares		0.0	0.0
Change in pension and postretirement liability, net of tax		$ 0.0	$ 0.0	0.0	0.0	2.2	0.0	2.2
Shares at Dec. 31, 2014		176.2
Treasury shares at Dec. 31, 2014			(0.8)
Balance at Dec. 31, 2014		$ 1.8	$ (25.4)	535.3	3,587.9	(24.3)	0.0	4,075.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 149.4	$ 0.0	$ 0.0	0.0	(149.4)	0.0	0.0	(149.4)
Stockholders' Equity, Other Shares		0.0	0.0
Dividends			0.0
Dividends		$ 0.0	$ 0.0	0.0	(14.1)	0.0	0.0	(14.1)
Share-based compensation		$ 0.0	$ 10.8	19.5	(6.1)	0.0	0.0	24.2
Share-based compensation, shares		1.1	0.3
Change in pension and postretirement liability, net of tax, shares		0.0	0.0
Change in pension and postretirement liability, net of tax		$ 0.0	$ 0.0	0.0	0.0	11.9	0.0	11.9
Shares at Dec. 31, 2015		177.3
Treasury shares at Dec. 31, 2015	(0.5)		(0.5)
Balance at Dec. 31, 2015	$ 3,947.9	$ 1.8	$ (14.6)	554.8	3,418.3	(12.4)	0.0	3,947.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 1,245.0	$ 0.0	$ 0.0	0.0	(1,245.0)	0.0	0.0	(1,245.0)
Stockholders' Equity, Other Shares		0.0	0.0
Dividends		0.0
Stock Issued During Period, Shares, New Issues		61.0	0.0
Stock Issued During Period, Value, New Issues		$ 0.6	$ 0.0	780.8	0.0	0.0	0.0	781.4
Share-based compensation		$ 0.0	$ (8.3)	31.0	0.0	0.0	0.0	22.7
Share-based compensation, shares		2.4	0.6
Change in pension and postretirement liability, net of tax, shares		0.0	0.0
Change in pension and postretirement liability, net of tax		$ 0.0	$ 0.0	0.0	0.0	(4.3)	0.0	(4.3)
Shares at Dec. 31, 2016		240.7
Treasury shares at Dec. 31, 2016	(1.1)		(1.1)
Balance at Dec. 31, 2016		$ 2.4	$ (22.9)	$ 1,366.6	$ 2,173.3	$ (16.7)	$ 0.0	$ 3,502.7