Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning balance at Dec. 31, 2019	$ 1,882.3	$ 1.4	$ 2,449.1	$ (229.8)	$ (338.4)
Balance, shares at Dec. 31, 2019		144,386,618
Net income (loss)	8.6			8.6
Issuance of common stock under share-based compensation plans	11.4		11.4
Issuance of common stock under share-based compensation plans, shares		551,328
Share-based compensation	12.5		12.5
Foreign currency translation	(49.1)				(49.1)
Change in unrealized gain, net of tax	17.4				17.4
Change in pension liability adjustment, net of tax	2.5				2.5
Ending balance at Mar. 31, 2020	1,885.6	$ 1.4	2,473.0	(221.2)	(367.6)
Balance, shares at Mar. 31, 2020		144,937,946
Beginning balance at Dec. 31, 2020	2,098.2	$ 1.5	2,606.5	(233.8)	(276.0)
Balance, shares at Dec. 31, 2020		148,571,412
Net income (loss)	(19.2)			(19.2)
Issuance of common stock under share-based compensation plans	11.3		11.3
Issuance of common stock under share-based compensation plans, shares		341,975
Share-based compensation	22.8		22.8
Equity component of convertible senior notes	77.7		77.7
Purchase of capped calls related to convertible senior notes	(33.0)		(33.0)
Foreign currency translation	11.0				11.0
Change in unrealized gain, net of tax	(12.3)				(12.3)
Change in pension liability adjustment, net of tax	2.8				2.8
Ending balance at Mar. 31, 2021	$ 2,159.3	$ 1.5	$ 2,685.3	$ (253.0)	$ (274.5)
Balance, shares at Mar. 31, 2021		148,913,387