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	82.8				82.8
Amortization of net actuarial losses and prior service credits, net of income taxes	14.0					14.0
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	(6.7)		(6.7)
Stock-based compensation and other, net (in shares)		0.6
Stock-based compensation and shares issued under equity plans	9.6		9.6
Ending balance (in shares) at Jun. 30, 2019		77.1
Ending balance at Jun. 30, 2019	521.0	$ 7.7	564.7	(12.7)	186.7	(225.4)
Beginning balance (in shares) at Mar. 31, 2019		77.1
Beginning balance at Mar. 31, 2019	466.2	$ 7.7	561.0	(12.7)	142.6	(232.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44.1				44.1
Amortization of net actuarial losses and prior service credits, net of income taxes	7.0					7.0
Contribution of treasury stock to retirement benefit plan	0.0
Repurchase of shares for withholding taxes and option costs under equity plans	(0.5)		(0.5)
Stock-based compensation and shares issued under equity plans	4.2		4.2
Ending balance (in shares) at Jun. 30, 2019		77.1
Ending balance at Jun. 30, 2019	521.0	$ 7.7	564.7	(12.7)	186.7	(225.4)
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	70.6				70.6
Amortization of net actuarial losses and prior service credits, net of income taxes	20.2					20.2
Purchase of treasury stock	(0.5)			(0.5)
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	(8.2)		(8.2)
Stock-based compensation and other, net (in shares)		0.5
Stock-based compensation and shares issued under equity plans	12.5		12.5
Ending balance (in shares) at Jun. 30, 2020		77.6
Ending balance at Jun. 30, 2020	671.3	$ 7.7	577.6	(13.2)	315.5	(216.3)
Beginning balance (in shares) at Mar. 31, 2020		77.6
Beginning balance at Mar. 31, 2020	616.8	$ 7.7	572.3	(13.2)	276.3	(226.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	39.2				39.2
Amortization of net actuarial losses and prior service credits, net of income taxes	10.0					10.0
Repurchase of shares for withholding taxes and option costs under equity plans (in shares)		(0.1)
Repurchase of shares for withholding taxes and option costs under equity plans	(0.3)		(0.3)
Stock-based compensation and other, net (in shares)		0.1
Stock-based compensation and shares issued under equity plans	5.6		5.6
Ending balance (in shares) at Jun. 30, 2020		77.6
Ending balance at Jun. 30, 2020	$ 671.3	$ 7.7	$ 577.6	$ (13.2)	$ 315.5	$ (216.3)