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]
Balance at Dec. 31, 2016	$ 3,502.7	$ 2.4	$ (22.9)	$ 1,366.6	$ 2,173.3	$ (16.7)
Shares at Dec. 31, 2016		240.7
Treasury shares at Dec. 31, 2016			(1.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	269.3				269.3
Share-based compensation, shares		2.3
Share-based compensation, treasury stock shares			(0.9)
Share-based compensation	20.3	$ 0.0	$ (11.3)	31.6	0.0	0.0
Change in pension and postretirement liability, net of tax	5.6					5.6
Balance at Dec. 31, 2017	3,797.9	$ 2.4	$ (34.2)	1,398.2	2,442.6	(11.1)
Shares at Dec. 31, 2017		243.0
Treasury shares at Dec. 31, 2017			(2.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(1,011.6)				(1,011.6)
Reclassification related to ASU 2018-02	0.0				3.8	(3.8)
Common stock repurchased and retired, Shares		(6.2)
Common stock repurchased and retired, Value	(58.4)	$ (0.1)			(58.3)
Share-based compensation, shares		3.0
Share-based compensation, treasury stock shares			(1.1)
Share-based compensation	22.4	$ 0.1	$ (11.4)	33.7	0.0	0.0
Change in pension and postretirement liability, net of tax	0.6					0.6
Balance at Dec. 31, 2018	$ 2,750.9	$ 2.4	$ (45.6)	1,431.9	1,376.5	(14.3)
Shares at Dec. 31, 2018		239.8
Treasury shares at Dec. 31, 2018	(3.1)		(3.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (97.3)				(97.3)
Cash dividends declared, $0.02 per share	(9.6)				(9.6)
Share-based compensation, shares		2.3
Share-based compensation, treasury stock shares			(1.3)
Share-based compensation	14.8	$ 0.0	$ (9.8)	24.6	0.0	0.0
Change in pension and postretirement liability, net of tax	1.8					1.8
Balance at Dec. 31, 2019	$ 2,660.6	$ 2.4	$ (55.4)	$ 1,456.5	$ 1,269.6	$ (12.5)
Shares at Dec. 31, 2019		242.1
Treasury shares at Dec. 31, 2019	(4.4)		(4.4)