Leases (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020
Lease Assets and Liabilities [Abstract]
Operating lease ROU assets		$ 63.3		$ 63.3		$ 61.4
Operating lease ROU assets, Statement of Financial Position [Extensible List]		us-gaap:OtherAssetsNoncurrent		us-gaap:OtherAssetsNoncurrent
Finance lease ROU assets	[1]	$ 8.5		$ 8.5		8.5
Finance lease ROU assets, Statement of Financial Position [Extensible List]		us-gaap:PropertyPlantAndEquipmentNet		us-gaap:PropertyPlantAndEquipmentNet
Operating lease liabilities, current		$ 12.6		$ 12.6		10.9
Operating lease liabilities, current, Statement of Financial Position [Extensible List]		us-gaap:OtherLiabilitiesCurrent		us-gaap:OtherLiabilitiesCurrent
Operating lease liabilities, Other noncurrent liabilities		$ 51.2		$ 51.2		50.3
Operating lease liabilities, noncurrent, Statement of Financial Position [Extensible List]		us-gaap:OtherLiabilitiesNoncurrent		us-gaap:OtherLiabilitiesNoncurrent
Finance lease liabilities, current		$ 0.4		$ 0.4		0.4
Finance lease liabilities, current, Statement of Financial Position [Extensible List]		us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent		us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
Finance lease liabilities, noncurrent		$ 3.3		$ 3.3		3.3
Finance lease liabilities, noncurrent, Statement of Financial Position [Extensible List]		us-gaap:LongTermDebtAndCapitalLeaseObligations		us-gaap:LongTermDebtAndCapitalLeaseObligations
Accumulated amortization		$ 2.1		$ 2.1		$ 1.8
Components of Lease Expense [Abstract]
Operating lease expense	[2]	5.2	$ 5.2	10.1	$ 10.4
Finance lease expense [Abstract]
Depreciation of ROU assets		0.1	0.1	0.2	0.2
Interest on lease liabilities		0.1	0.1	0.1	0.1
Total lease expense		5.4	5.4	10.4	10.7
Short-term lease expense		$ 0.9	$ 1.0	$ 1.8	$ 1.9

[1] Finance lease right of use (“ROU”) assets were recorded net of accumulated amortization of $2.1 million and $1.8 million as of September 30, 2020 and March 31, 2020, respectively.

[2] For the three and six months ended September 30, 2020, operating lease expense included short-term lease expense of $0.9 million and $1.8 million, respectively.  For the three and six months ended September 30, 2019, operating lease expense included short-term lease expense of $1.0 million and $1.9 million, respectively. Variable lease expense was not significant.