Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Other Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2018		76.8
Beginning balance at Dec. 31, 2018	$ 421.3	$ 7.7	$ 561.8	$ (12.7)	$ 103.9	$ (239.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	115.7				115.7
Amortization of net actuarial losses, net of income taxes	20.9					20.9
Repurchase of shares for withholding taxes and option costs under equity plans (in shares)		(0.3)
Repurchase of shares for withholding taxes and option costs under equity plans	(7.5)		(7.5)
Stock-based compensation and other, net (in shares)		0.8
Stock-based compensation and shares issued under equity plans	16.3		16.3
Ending balance (in shares) at Sep. 30, 2019		77.3
Ending balance at Sep. 30, 2019	566.7	$ 7.7	570.6	(12.7)	219.6	(218.5)
Beginning balance (in shares) at Jun. 30, 2019		77.1
Beginning balance at Jun. 30, 2019	521.0	$ 7.7	564.7	(12.7)	186.7	(225.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	32.9				32.9
Amortization of net actuarial losses, net of income taxes	6.9					6.9
Repurchase of shares for withholding taxes and option costs under equity plans	(0.8)		(0.8)
Stock-based compensation and other, net (in shares)		0.2
Stock-based compensation and shares issued under equity plans	6.7		6.7
Ending balance (in shares) at Sep. 30, 2019		77.3
Ending balance at Sep. 30, 2019	566.7	$ 7.7	570.6	(12.7)	219.6	(218.5)
Beginning balance (in shares) at Dec. 31, 2019		77.3
Beginning balance at Dec. 31, 2019	576.7	$ 7.7	573.3	(12.7)	244.9	(236.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	102.3				102.3
Amortization of net actuarial losses, net of income taxes	$ 30.3					30.3
Purchase of treasury stock (in shares)	(0.3)
Purchase of treasury stock	$ (12.3)			(12.3)
Repurchase of shares for withholding taxes and option costs under equity plans (in shares)		(0.2)
Repurchase of shares for withholding taxes and option costs under equity plans	(8.8)		(8.8)
Stock-based compensation and other, net (in shares)		0.6
Stock-based compensation and shares issued under equity plans	20.7		20.7
Ending balance (in shares) at Sep. 30, 2020		77.4
Ending balance at Sep. 30, 2020	708.9	$ 7.7	585.2	(25.0)	347.2	(206.2)
Beginning balance (in shares) at Jun. 30, 2020		77.6
Beginning balance at Jun. 30, 2020	671.3	$ 7.7	577.6	(13.2)	315.5	(216.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	31.7				31.7
Amortization of net actuarial losses, net of income taxes	$ 10.1					10.1
Purchase of treasury stock (in shares)	(0.3)
Purchase of treasury stock	$ (11.8)			(11.8)
Repurchase of shares for withholding taxes and option costs under equity plans	(0.6)		(0.6)
Stock-based compensation and other, net (in shares)		0.1
Stock-based compensation and shares issued under equity plans	8.2		8.2
Ending balance (in shares) at Sep. 30, 2020		77.4
Ending balance at Sep. 30, 2020	$ 708.9	$ 7.7	$ 585.2	$ (25.0)	$ 347.2	$ (206.2)