Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		12 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		$ 376.2
Other comprehensive income (loss) before reclassifications		(11.1)	$ (11.9)
Reclassifications [Abstract]
Reclassifications for amortization of unrecognized net loss	[1]	5.2	48.3
Amortization of unrecognized prior service credit	[1]		(0.2)
Income taxes		(1.7)	(11.8)
Total other comprehensive income (loss)		(7.6)	24.4
Ending balance		414.0	376.2
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(174.2)	(198.6)
Reclassifications [Abstract]
Ending balance		(181.8)	(174.2)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(36.0)	(40.7)
Other comprehensive income (loss) before reclassifications		(10.8)	4.7
Reclassifications [Abstract]
Reclassifications for amortization of unrecognized net loss	[1]	0.0	0.0
Amortization of unrecognized prior service credit	[1]		0.0
Income taxes		0.0	0.0
Total other comprehensive income (loss)		(10.8)	4.7
Ending balance		(46.8)	(36.0)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Loss [Line Items]
Beginning balance		(138.2)	(157.9)
Other comprehensive income (loss) before reclassifications		(0.3)	(16.6)
Reclassifications [Abstract]
Reclassifications for amortization of unrecognized net loss	[1]	5.2	48.3
Amortization of unrecognized prior service credit	[1]		(0.2)
Income taxes		(1.7)	(11.8)
Total other comprehensive income (loss)		3.2	19.7
Ending balance		$ (135.0)	$ (138.2)

[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.