Consolidated Statement of Shareholders' Equity - USD ($) $ in Millions	Total	Ordinary Shares	Additional Paid-in Capital	Treasury Shares	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total Equity of MKHL	Non-controlling Interests
Beginning balance at Apr. 01, 2017					$ (80.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 328.2
Other comprehensive loss					21.0
Comprehensive income	349.2
Ending balance at Sep. 30, 2017					(59.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of accounting standards	11.7					$ 11.7	$ 11.7
Balance as of April 1, 2018	$ 2,033.2		$ 831.1	$ (3,015.9)	50.5	4,163.7	2,029.4	$ 3.8
Beginning balance (in shares) at Mar. 31, 2018	210,991,091	210,991,000
Beginning balance (in shares) at Mar. 31, 2018	(61,292,684)			(61,293,000)
Beginning balance at Mar. 31, 2018	$ 2,021.5	$ 0.0	831.1	$ (3,015.9)	50.5	4,152.0	2,017.7	3.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	323.3					324.0	324.0	(0.7)
Other comprehensive loss	(113.5)				(113.4)		(113.4)	(0.1)
Comprehensive income	209.8						210.6	(0.8)
Vesting of restricted awards, net of forfeitures (in shares)		697,000
Exercises of employee share options (in shares)		1,521,000
Exercise of employee share options	20.4		20.4				20.4
Equity compensation expense	26.4		26.4				26.4
Purchase of treasury shares (in shares)				(1,766,000)
Purchase of treasury shares	(107.1)			$ (107.1)			(107.1)
Increase in noncontrolling interest	$ 0.6							0.6
Ending balance (in shares) at Sep. 29, 2018	213,208,924	213,209,000
Ending balance (in shares) at Sep. 29, 2018	(63,058,627)			(63,059,000)
Ending balance at Sep. 29, 2018	$ 2,183.3	$ 0.0	$ 877.9	$ (3,123.0)	$ (62.9)	$ 4,487.7	$ 2,179.7	$ 3.6