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, 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					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)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 3.2				3.2
Cash dividends declared, $0.02 per share	(4.8)				(4.8)
Share-based compensation, shares		5.9
Share-based compensation, treasury stock shares			(1.0)
Share-based compensation	11.5	$ 0.1	$ (2.2)	13.6	0.0	0.0
Change in pension and postretirement liability, net of tax	(0.3)					(0.3)
Balance at Dec. 31, 2020	$ 2,670.2	$ 2.5	$ (57.6)	$ 1,470.1	$ 1,268.0	$ (12.8)
Shares at Dec. 31, 2020		248.0
Treasury shares at Dec. 31, 2020	(5.4)		(5.4)