Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Amortizing Intangibles:
Amortization charges	$ 4.5	$ 4.5	$ 4.3
Finite-Lived Intangible Assets, Amortization Expense, Year Two	4.5
Amortization expense, year four	4.5
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	11.9
Patents [Member]
Amortizing Intangibles:
Amortization charges	1.4	1.4	1.4
Finite-Lived Intangible Assets, Amortization Expense, Year Two	1.4
Amortization expense, year four	1.4
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	6.1
Customer Relationships
Amortizing Intangibles:
Amortization charges	$ 3.1	$ 3.1	$ 2.9
Useful life	12 years 2 months 12 days	12 years 3 months 12 days
Finite-Lived Intangible Assets, Amortization Expense, Year Two	$ 3.1
Amortization expense, year four	3.1
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	$ 5.8
Purchased technology, customer relationships and patents | Weighted Average [Member]
Amortizing Intangibles:
Useful life	15 years 9 months 18 days	15 years 9 months 6 days
Finite-Lived Intangible Asset, Weighted Average Period before Next Renewal or Extension	1 year 6 months	2 years 6 months