Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		12 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		$ 414.0
Other comprehensive income (loss) before reclassifications		35.9	$ (11.1)
Reclassifications for amortization of unrecognized net loss	[1]	5.6	5.2
Reclassifications of realized gains	[2]	(0.1)
Income taxes		0.1	(1.7)
Total other comprehensive income (loss)		41.5	(7.6)
Ending balance		490.1	414.0
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(181.8)	(174.2)
Ending balance		(140.3)	(181.8)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(46.8)	(36.0)
Other comprehensive income (loss) before reclassifications		41.3	(10.8)
Reclassifications for amortization of unrecognized net loss	[1]	0.0	0.0
Reclassifications of realized gains	[2]	0.0
Income taxes		0.0	0.0
Total other comprehensive income (loss)		41.3	(10.8)
Ending balance		(5.5)	(46.8)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(135.0)	(138.2)
Other comprehensive income (loss) before reclassifications		(5.7)	(0.3)
Reclassifications for amortization of unrecognized net loss	[1]	5.6	5.2
Reclassifications of realized gains	[2]	0.0
Income taxes		0.2	(1.7)
Total other comprehensive income (loss)		0.1	3.2
Ending balance		(134.9)	(135.0)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		0.0
Other comprehensive income (loss) before reclassifications		0.3
Reclassifications for amortization of unrecognized net loss	[1]	0.0
Reclassifications of realized gains	[2]	(0.1)
Income taxes		(0.1)
Total other comprehensive income (loss)		0.1
Ending balance		$ 0.1	$ 0.0

[1] Amounts are included in the calculation of net periodic benefit cost for the Company's defined benefit plans, which include pension and other postretirement plans. See Note 16 for additional information about the Company's pension plans.

[2] Amounts reclassified to net earnings. See Note 17 for additional information regarding derivative instruments.