Condensed Consolidated Statements of Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Retained Earnings Cumulative Effect Period Of Adoption Adjustment	Treasury Stock
Balance at beginning of period at Dec. 31, 2019		$ 0.4	$ 592.2	$ (121.0)	$ 236.2	$ (0.2)	$ (61.9)
Increase (Decrease) in Stockholders' Equity
Stock options exercised and issuance of other stock awards			(2.1)				1.8
Common stock repurchases							12.0
Stock-based compensation			5.9
Other comprehensive income (loss)				(3.1)
Net income (loss)	$ (20.5)				(20.5)
Common stock repurchases							(12.0)
Balance at end of period at Jun. 30, 2020	615.7	0.4	596.0	(124.1)	215.5		(72.1)
Balance at beginning of period at Mar. 31, 2020		0.4	593.7	(133.4)	228.2		(72.2)
Increase (Decrease) in Stockholders' Equity
Stock options exercised and issuance of other stock awards			(0.2)				0.1
Stock-based compensation			2.5
Other comprehensive income (loss)				9.3
Net income (loss)	(12.7)				(12.7)
Balance at end of period at Jun. 30, 2020	615.7	0.4	596.0	(124.1)	215.5		(72.1)
Balance at beginning of period at Dec. 31, 2020		0.4	595.1	(97.5)	216.9		(71.4)
Increase (Decrease) in Stockholders' Equity
Stock options exercised and issuance of other stock awards			0.2				4.9
Common stock repurchases		10.6
Stock-based compensation			4.8
Other comprehensive income (loss)				(12.0)
Net income (loss)	14.8				14.8
Common stock repurchases		(10.6)
Balance at end of period at Jun. 30, 2021	656.2	0.4	600.1	(109.5)	231.7		(66.5)
Balance at beginning of period at Mar. 31, 2021		0.4	596.4	(108.1)	213.8		(69.5)
Increase (Decrease) in Stockholders' Equity
Stock options exercised and issuance of other stock awards			1.4				3.0
Stock-based compensation			2.3
Other comprehensive income (loss)				(1.4)
Net income (loss)	17.9				17.9
Balance at end of period at Jun. 30, 2021	$ 656.2	$ 0.4	$ 600.1	$ (109.5)	$ 231.7		$ (66.5)