Recently Issued Accounting Pronouncements Topic 606 (Details) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Apr. 01, 2018	Mar. 31, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales		$ 1,212.5	$ 972.1
Cost of Goods Sold	[1]	570.5	387.7
Gross Profit		642.0	584.4
Income tax provision (benefit)		2.0	(4.4)
Net income		35.7	$ 170.6
Accounts Receivable, Net, Current		789.4		$ 518.1	$ 563.7
Inventories		1,104.8		471.1	476.2
Other Assets, Current		274.5		73.1	119.8
Long-term deferred tax assets		1,675.8		1,656.5	100.2
Accrued liabilities		491.3		248.1	229.6
Deferred income on shipments to distributors		0.0		0.0	333.8
Long-term deferred tax liability		854.2		221.5	205.8
Retained earnings		3,149.2		$ 3,199.0	1,397.3
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts Receivable, Net, Current					(45.6)
Inventories					(5.1)
Other Assets, Current					17.2
Long-term deferred tax assets					(23.1)
Accrued liabilities					18.5
Deferred income on shipments to distributors					(333.8)
Long-term deferred tax liability					16.8
Retained earnings					$ 241.9
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales		1,210.0
Cost of Goods Sold	[1]	571.7
Gross Profit		638.3
Income tax provision (benefit)		(0.3)
Net income		34.3
Accounts Receivable, Net, Current		845.7
Inventories		1,109.9
Other Assets, Current		256.8
Long-term deferred tax assets		1,700.5
Accrued liabilities		471.2
Deferred income on shipments to distributors		349.5
Long-term deferred tax liability		837.4
Retained earnings		2,905.0
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net sales		2.5
Cost of Goods Sold	[1]	(1.2)
Gross Profit		3.7
Income tax provision (benefit)		2.3
Net income		1.4
Accounts Receivable, Net, Current		(56.3)
Inventories		(5.1)
Other Assets, Current		17.7
Long-term deferred tax assets		(24.7)
Accrued liabilities		20.1
Deferred income on shipments to distributors		(349.5)
Long-term deferred tax liability		16.8
Retained earnings		$ 244.2

[1] Includes share-based compensation expense as follows:Cost of sales 3.6 3.4 Research and development 14.1 10.3 Selling, general and administrative 11.7 8.7Special charges and other, net 15.9 0