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	94.8			90.1			4.7
Other comprehensive income (loss)	51.0					49.4	1.6
Employee stock plans	1.2		(10.8)	(0.3)	12.3
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
Total Stockholders' Equity at Mar. 31, 2019	2,046.6	12.7	1,599.7	1,437.0	(19.7)	(1,095.5)	112.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	78.5			75.1			3.4
Other comprehensive income (loss)	7.5					11.1	(3.6)
Employee stock plans	6.0		4.9	(0.3)	1.4
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
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	(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	(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