STATEMENTS OF CHANGES IN CONSOLIDATED EQUITY - USD ($) $ in Millions	Total	[CommonStockMember]	Additional Paid-in Capital [Member]	[RetainedEarningsMember]	[TreasuryStockMember]	[AccumulatedOtherComprehensiveIncomeMember]	[NoncontrollingInterestMember]
Total Stockholders' Equity at Dec. 31, 2019	$ 2,193.2	$ 12.7	$ 1,618.0	$ 1,679.3	$ (18.2)	$ (1,201.7)	$ 103.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(396.3)			(401.5)			5.2
Other comprehensive income (loss)	27.6					28.9	(1.3)
Equity component of convertible note	48.7		48.7
Convertible note capped call	(19.0)		(19.0)
Employee stock plans	(11.9)		(29.9)	(0.2)	18.2
Total Stockholders' Equity at Jun. 30, 2020	1,842.3	12.7	1,617.8	1,277.6	0.0	(1,172.8)	107.0
Total Stockholders' Equity at Mar. 31, 2020	2,192.6	12.7	1,592.1	1,700.4	(0.8)	(1,216.6)	104.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(419.9)			(422.6)			2.7
Other comprehensive income (loss)	43.3					43.8	(0.5)
Equity component of convertible note	48.7		48.7
Convertible note capped call	(19.0)		(19.0)
Employee stock plans	(3.4)		(4.0)	(0.2)	0.8
Total Stockholders' Equity at Jun. 30, 2020	1,842.3	12.7	1,617.8	1,277.6	0.0	(1,172.8)	107.0
Total Stockholders' Equity at Dec. 31, 2020	641.4	12.7	1,625.5	106.5	0.0	(1,223.6)	120.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(46.8)			(57.1)			10.3
Other comprehensive income (loss)	49.8					47.3	2.5
Employee stock plans	7.1		11.8	0.0	(4.7)
Total Stockholders' Equity at Jun. 30, 2021	606.1	12.7	1,587.5	53.8	(4.7)	(1,176.3)	133.1
Total Stockholders' Equity at Mar. 31, 2021	609.3	12.7	1,580.5	103.0	(4.7)	(1,208.6)	126.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(44.4)			(49.2)			4.8
Other comprehensive income (loss)	34.2					32.3	1.9
Employee stock plans	7.0		7.0	0.0	0.0
Total Stockholders' Equity at Jun. 30, 2021	$ 606.1	$ 12.7	$ 1,587.5	$ 53.8	$ (4.7)	$ (1,176.3)	$ 133.1