CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock and Additional Paid-in-Capital	Common Stock Held in Treasury	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment
Balance, common stock shares issued (in shares) at Mar. 31, 2018			253,200,000
Beginning balance at Mar. 31, 2018	$ 3,279.8		$ 2,562.7	$ (662.6)	$ (17.6)		$ 1,397.3
Beginning balance (Accounting Standards Update 2016-01) at Mar. 31, 2018						$ (1.7)		$ 1.7
Beginning balance (Accounting Standards Update 2014-09) at Mar. 31, 2018		$ 242.0						242.0
Beginning balance (Accounting Standards Update 2016-16) at Mar. 31, 2018		$ 1,558.1						1,558.1
Balance, common stock held in treasury (in shares) at Mar. 31, 2018				18,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	355.9						355.9
Other comprehensive income (loss)	(1.4)				(1.4)
Non-cash consideration, exchange of employee stock awards - Microsemi acquisition	53.9		$ 53.9
Proceeds from sales of common stock through employee equity incentive plans (shares)			3,400,000
Proceeds from sales of common stock through employee equity incentive plans	42.6		$ 42.6
Restricted stock unit and stock appreciation right withholdings (shares)			(800,000)
Restricted stock unit and stock appreciation right withholdings	(71.8)		$ (71.8)
Treasury stock used for new issuances (shares)			(2,600,000)	(2,600,000)
Treasury stock used for new issuances			$ (80.4)	$ 80.4
Share-based compensation	172.8		$ 172.8
Cash dividend	(344.4)						(344.4)
Balance, common stock shares issued (in shares) at Mar. 31, 2019			253,200,000
Ending balance at Mar. 31, 2019	5,287.5		$ 2,679.8	$ (582.2)	(20.7)	(1.3)	3,210.6
Ending balance (Accounting Standards Update 2018-02) at Mar. 31, 2019						$ (1.3)		$ 1.3
Balance, common stock held in treasury (in shares) at Mar. 31, 2019				15,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	570.6						570.6
Other comprehensive income (loss)	0.4				0.4
Proceeds from sales of common stock through employee equity incentive plans (shares)			3,200,000
Proceeds from sales of common stock through employee equity incentive plans	58.8		$ 58.8
Restricted stock unit and stock appreciation right withholdings (shares)			(700,000)
Restricted stock unit and stock appreciation right withholdings	(68.1)		$ (68.1)
Treasury stock used for new issuances (shares)			(2,500,000)	(2,500,000)
Treasury stock used for new issuances			$ (81.6)	$ 81.6
Shares issued to settle convertible debt (in shares)			5,200,000
Value of Shares Issued	351.8		$ 351.8
Settlement of convertible debt	(438.1)		(438.1)
Share-based compensation	172.7		$ 172.7
Cash dividend	$ (350.1)						(350.1)
Balance, common stock shares issued (in shares) at Mar. 31, 2020	258,391,231		258,400,000
Ending balance at Mar. 31, 2020	$ 5,585.5		$ 2,675.3	$ (500.6)	(21.6)		3,432.4
Balance, common stock held in treasury (in shares) at Mar. 31, 2020	13,065,588			13,100,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 349.4						349.4
Other comprehensive income (loss)	(4.6)				(4.6)
Proceeds from sales of common stock through employee equity incentive plans (shares)			2,600,000
Proceeds from sales of common stock through employee equity incentive plans	60.3		$ 60.3
Restricted stock unit and stock appreciation right withholdings (shares)			(500,000)
Restricted stock unit and stock appreciation right withholdings	(64.6)		$ (64.6)
Treasury stock used for new issuances (shares)			(2,100,000)	(2,100,000)
Treasury stock used for new issuances			$ (66.8)	$ 66.8
Shares issued to settle convertible debt (in shares)			26,100,000
Value of Shares Issued	3,171.1		$ 3,171.1
Settlement of convertible debt	(3,622.1)		(3,622.1)
Purchase of capped call options	(35.8)		(35.8)
Issuance of 2020 Senior Convertible Debt	87.7		87.7
Share-based compensation	198.5		$ 198.5
Cash dividend	$ (388.3)						(388.3)
Balance, common stock shares issued (in shares) at Mar. 31, 2021	284,479,079		284,500,000
Ending balance at Mar. 31, 2021	$ 5,337.1		$ 2,403.6	$ (433.8)	$ (26.2)		$ 3,393.5
Balance, common stock held in treasury (in shares) at Mar. 31, 2021	10,950,485			11,000,000.0