Recently Issued Accounting Pronouncements (Details) - USD ($) $ in Millions	Jun. 30, 2018	Apr. 01, 2018	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Net, Current	$ 789.4	$ 518.1	$ 563.7
Inventories	1,104.8	471.1	476.2
Long-term deferred tax assets	1,675.8	1,656.5	100.2
Other assets	154.1	47.7	71.8
Accrued liabilities	491.3	248.1	229.6
Deferred income on shipments to distributors	0.0	0.0	333.8
Other Assets, Current	(274.5)	(73.1)	(119.8)
Long-term deferred tax liability	(854.2)	(221.5)	(205.8)
Other long-term liabilities	(275.0)	(239.2)	(240.9)
Accumulated other comprehensive loss	(14.9)	(19.3)	(17.6)
Retained earnings	$ 3,149.2	$ 3,199.0	1,397.3
Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Net, Current			563.7
Inventories			476.2
Long-term deferred tax assets			100.2
Other assets			71.8
Accrued liabilities			229.6
Deferred income on shipments to distributors			333.8
Other Assets, Current			(55.9)
Long-term deferred tax liability			(205.8)
Other long-term liabilities			(240.9)
Accumulated other comprehensive loss			(17.6)
Retained earnings			1,397.3
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts Receivable, Net, Current			(45.6)
Inventories			(5.1)
Long-term deferred tax assets			(23.1)
Accrued liabilities			18.5
Deferred income on shipments to distributors			(333.8)
Other Assets, Current			(17.2)
Long-term deferred tax liability			(16.8)
Accumulated other comprehensive loss			0.0
Retained earnings			241.9
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated other comprehensive loss			(1.7)
Retained earnings			1.7
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term deferred tax assets			1,579.4
Other assets			(24.1)
Long-term deferred tax liability			1.1
Other long-term liabilities			1.7
Accumulated other comprehensive loss			0.0
Retained earnings			$ 1,558.1