Leases - Components of Lease Expense (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lease Cost
Operating lease cost	$ 1.3	$ 2.4	$ 3.9	$ 7.0
Financing lease cost:
Depreciation of lease assets	0.3	0.2	1.0	0.6
Interest on lease liabilities	0.1	0.1	0.2	0.3
Sublease income	(0.6)	(1.1)	(1.9)	(3.2)
Total lease cost, net	$ 1.1	$ 1.6	$ 3.2	$ 4.7