Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance				$ 414.0
Other comprehensive income (loss) before reclassifications		$ 11.3	$ 1.8	27.8	$ (3.0)
Reclassifications for amortization of unrecognized net loss	[1]	1.3	1.3	2.6	2.6
Income taxes		(0.4)	(0.5)	(0.9)	(0.9)
Total other comprehensive income (loss)		12.2	2.6	29.5	(1.3)
Ending balance		482.5		482.5
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(164.5)	(178.1)	(181.8)	(174.2)
Ending balance		(152.3)	(175.5)	(152.3)	(175.5)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(30.3)	(40.8)	(46.8)	(36.0)
Other comprehensive income (loss) before reclassifications		11.3	1.8	27.8	(3.0)
Reclassifications for amortization of unrecognized net loss	[1]	0.0	0.0	0.0	0.0
Income taxes		0.0	0.0	0.0	0.0
Total other comprehensive income (loss)		11.3	1.8	27.8	(3.0)
Ending balance		(19.0)	(39.0)	(19.0)	(39.0)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(134.2)	(137.3)	(135.0)	(138.2)
Other comprehensive income (loss) before reclassifications		0.0	0.0	0.0	0.0
Reclassifications for amortization of unrecognized net loss	[1]	1.3	1.3	2.6	2.6
Income taxes		(0.4)	(0.5)	(0.9)	(0.9)
Total other comprehensive income (loss)		0.9	0.8	1.7	1.7
Ending balance		$ (133.3)	$ (136.5)	$ (133.3)	$ (136.5)

[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 4 for additional information about the Company's pension plans.