CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Stock and Additional Paid-in-Capital	Common Stock Held in Treasury	Accumulated Other Comprehensive Income	Retained Earnings
Balance, common stock shares issued (in shares) at Mar. 31, 2018		253,200,000
Balance at Mar. 31, 2018	$ 3,279.8	$ 2,562.7	$ (662.6)	$ (17.6)	$ 1,397.3
Balance, common stock held in treasury (in shares) at Mar. 31, 2018			18,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	35.7				35.7
Other comprehensive income	4.4			4.4
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)		700,000
Proceeds from sales of common stock through employee equity incentive plans	6.4	$ 6.4
Restricted stock unit and stock appreciation right withholdings (shares)		(200,000)
Restricted stock unit and stock appreciation right withholdings	(16.8)	$ (16.8)
Treasury stock used for new issuances (shares)		(500,000)	(500,000)
Treasury stock used for new issuances	0.0	$ (14.9)	$ 14.9
Share-based compensation	45.9	$ 45.9
Cash dividend	(85.5)				(85.5)
Balance, common stock shares issued (in shares) at Jun. 30, 2018		253,200,000
Balance at Jun. 30, 2018	$ 5,123.8	$ 2,637.2	$ (647.7)	(14.9)	3,149.2
Balance, common stock held in treasury (in shares) at Jun. 30, 2018			17,700,000
Balance, common stock shares issued (in shares) at Mar. 31, 2019	253,232,909	253,200,000
Balance at Mar. 31, 2019	$ 5,287.5	$ 2,679.8	$ (582.2)	(20.7)	3,210.6
Balance, common stock held in treasury (in shares) at Mar. 31, 2019	15,643,408		15,600,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 50.7				50.7
Other comprehensive income	(0.3)			(0.3)
Proceeds from sales of common stock through employee equity incentive plans (shares)		500,000
Proceeds from sales of common stock through employee equity incentive plans	7.3	$ 7.3
Restricted stock unit and stock appreciation right withholdings (shares)		(100,000)
Restricted stock unit and stock appreciation right withholdings	(11.4)	$ (11.4)
Treasury stock used for new issuances (shares)		(400,000)	(400,000)
Treasury stock used for new issuances	0.0	$ (13.8)	$ 13.8
Share-based compensation	41.6	$ 41.6
Cash dividend	$ (87.1)				(87.1)
Balance, common stock shares issued (in shares) at Jun. 30, 2019	253,232,909	253,200,000
Balance at Jun. 30, 2019	$ 5,288.3	$ 2,703.5	$ (568.4)	$ (22.3)	$ 3,175.5
Balance, common stock held in treasury (in shares) at Jun. 30, 2019	15,198,090		15,200,000