Supplemental Financial Information - Comprehensive Income (Schedule of Changes in the Components of AOCI) (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 01, 2018	Mar. 31, 2019	Mar. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive loss before reclassifications		$ (8.0)	$ (19.2)
Amounts reclassified from accumulated other comprehensive income (loss)		6.6	16.0
Net other comprehensive loss		(1.4)	(3.2)
Unrealized Holding Gains (Losses) Available-for-sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 1.9	1.9	0.3
Impact of change in accounting principle	(1.7)
Other comprehensive loss before reclassifications		(5.6)	(13.6)
Amounts reclassified from accumulated other comprehensive income (loss)		5.6	15.2
Net other comprehensive loss		0.0	1.6
Ending Balance	0.2	0.2	1.9
Minimum Pension Liability
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(10.1)	(10.1)	(5.3)
Impact of change in accounting principle	0.0
Other comprehensive loss before reclassifications		2.9	(5.6)
Amounts reclassified from accumulated other comprehensive income (loss)		1.0	0.8
Net other comprehensive loss		3.9	(4.8)
Ending Balance	(10.1)	(6.2)	(10.1)
Foreign Currency
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(9.4)	(9.4)	(9.4)
Impact of change in accounting principle	0.0
Other comprehensive loss before reclassifications		(5.3)	0.0
Amounts reclassified from accumulated other comprehensive income (loss)		0.0	0.0
Net other comprehensive loss		(5.3)	0.0
Ending Balance	(9.4)	(14.7)	(9.4)
Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(17.6)	(17.6)	(14.4)
Impact of change in accounting principle	(1.7)
Ending Balance	$ (19.3)	$ (20.7)	$ (17.6)