Significant Accounting Policies - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 1,231.0	$ 1,212.8	$ 1,070.6
Ending balance	1,313.7	1,231.0	1,212.8
Interest Rate Derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	0.8	(3.7)	(9.5)
Other comprehensive (loss) income before reclassifications	0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	4.5	5.8
Net current period other comprehensive income (loss)	0.0	4.5	5.8
Ending balance	0.8	0.8	(3.7)
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(60.1)	(42.2)	(99.3)
Other comprehensive (loss) income before reclassifications	(24.5)	(39.4)	57.1
Amounts reclassified from accumulated other comprehensive income (loss)	0.0	21.5	0.0
Net current period other comprehensive income (loss)	(24.5)	(17.9)	57.1
Ending balance	(84.6)	(60.1)	(42.2)
Pension and Postretirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(37.3)	(28.2)	(28.2)
Other comprehensive (loss) income before reclassifications	(3.6)	(8.5)	1.4
Amounts reclassified from accumulated other comprehensive income (loss)	0.3	(0.6)	(1.4)
Net current period other comprehensive income (loss)	(3.3)	(9.1)	0.0
Ending balance	(40.6)	(37.3)	(28.2)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(96.6)	(74.1)	(137.0)
Other comprehensive (loss) income before reclassifications	(28.1)	(47.9)	58.5
Amounts reclassified from accumulated other comprehensive income (loss)	0.3	25.4	4.4
Net current period other comprehensive income (loss)	(27.8)	(22.5)	62.9
Ending balance	$ (124.4)	$ (96.6)	$ (74.1)