STATEMENTS OF CHANGES IN CONSOLIDATED EQUITY - USD ($) $ in Millions	Total	[CommonStockMember]	[AdditionalPaidInCapitalMember]	[RetainedEarningsMember]	[TreasuryStockMember]	[AccumulatedOtherComprehensiveIncomeMember]	[NoncontrollingInterestMember]
Total Stockholders' Equity at Dec. 31, 2018	$ 1,991.6	$ 12.7	$ 1,615.4	$ 1,422.0	$ (30.6)	$ (1,133.8)	$ 105.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	210.1			201.1			9.0
Other comprehensive income (loss)	69.4					72.4	(3.0)
Employee stock plans	8.8		(3.3)	(0.3)	12.4
Total Stockholders' Equity at Sep. 30, 2019	2,279.9	12.7	1,612.1	1,622.8	(18.2)	(1,061.4)	111.9
Total Stockholders' Equity at Jun. 30, 2019	2,138.6	12.7	1,604.6	1,511.8	(18.3)	(1,084.4)	112.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	115.3			111.0			4.3
Other comprehensive income (loss)	18.4					23.0	(4.6)
Employee stock plans	7.6		7.5	0.0	0.1
Total Stockholders' Equity at Sep. 30, 2019	2,279.9	12.7	1,612.1	1,622.8	(18.2)	(1,061.4)	111.9
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)	(443.3)			(451.6)			8.3
Other comprehensive income (loss)	77.8					73.1	4.7
Equity component of convertible note	49.8		49.8
Convertible note capped call	(19.4)		(19.4)
Employee stock plans	(8.3)		(26.2)	(0.3)	18.2
Total Stockholders' Equity at Sep. 30, 2020	1,849.8	12.7	1,622.2	1,227.4	0.0	(1,128.6)	116.1
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(47.0)			(50.1)			3.1
Other comprehensive income (loss)	50.2					44.2	6.0
Equity component of convertible note	1.1		1.1
Convertible note capped call	(0.4)		(0.4)
Employee stock plans	3.6		3.7	(0.1)	0.0
Total Stockholders' Equity at Sep. 30, 2020	$ 1,849.8	$ 12.7	$ 1,622.2	$ 1,227.4	$ 0.0	$ (1,128.6)	$ 116.1