Leases (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Dec. 31, 2019	Dec. 31, 2019	Mar. 31, 2019	Mar. 31, 2018
Lease Assets [Abstract]
Right-of-use assets		$ 64.3	$ 64.3	$ 61.3
Finance lease ROU assets, Property, plant and equipment - net	[1]	8.6	8.6
Lease Liabilities [Abstract]
Operating lease liabilities, Other current liabilities		11.1	11.1
Operating lease liabilities, Other noncurrent liabilities		52.9	52.9
Finance lease liabilities, Long-term debt - current portion		0.4	0.4
Finance lease liabilities, Long-term debt		3.4	3.4
Accumulated amortization		1.7	1.7
Components of Lease Expense [Abstract]
Operating lease expense	[2]	5.4	15.8
Finance lease expense [Abstract]
Depreciation of ROU assets		0.2	0.4
Interest on lease liabilities		0.0	0.1
Total lease expense		5.6	16.3
Short-term lease expense		1.0	2.9
Cash paid for amounts included in measurement of lease liabilities [Abstract]
Operating cash flows for operating leases		3.0	10.9
Financing cash flows for finance leases		0.2	0.4
ROU assets obtained in exchange for lease liabilities [Abstract]
Operating leases		1.9	7.3
Finance leases		$ 0.0	$ 0.1
Weighted-average remaining lease term [Abstract]
Operating leases		9 years 4 months 24 days	9 years 4 months 24 days
Finance leases		9 years 1 month 6 days	9 years 1 month 6 days
Weighted-average discount rate [Abstract]
Operating leases		3.50%	3.50%
Finance leases		4.80%	4.80%
Maturity of Operating Lease Liabilities [Abstract]
Remainder of fiscal 2020		$ 3.4	$ 3.4
2021		12.8	12.8
2022		11.1	11.1
2023		9.1	9.1
2024		6.4	6.4
2025 and beyond		32.6	32.6
Total lease payments		75.4	75.4
Less: Interest		(11.4)	(11.4)
Present value of lease liabilities		64.0	64.0
Maturities of Finance Lease Liabilities [Abstract]
Remainder of fiscal 2020		0.1	0.1
2021		0.5	0.5
2022		0.5	0.5
2023		0.5	0.5
2024		0.5	0.5
2025 and beyond		2.6	2.6
Total lease payments		4.7	4.7
Less: Interest		(0.9)	(0.9)
Present value of lease liabilities		$ 3.8	$ 3.8
Future minimum rental commitments under non-cancelable operating leases [Abstract]
2020				14.2
2021				12.4
2022				9.1
2023				7.1
2024				4.7
2025 and beyond				22.9
Total future minimum rental commitments				70.4
Rental expense				$ 19.3	$ 18.5
Minimum [Member]
Significant Accounting Policy [Abstract]
Remaining lease term			1 year
Maximum [Member]
Significant Accounting Policy [Abstract]
Remaining lease term			15 years

[1] Finance lease ROU assets were recorded net of accumulated amortization of $1.7 million as of December 31, 2019.

[2] For the three and nine months ended December 31, 2019, operating lease expense included short-term lease expense of $1.0 million and $2.9 million, respectively. Variable lease expense was not significant.