Derivative Instruments and Hedging Activities (Forward Contracts by Balance Sheet Location) (Details) - Designated as Hedging Instrument - USD ($) $ in Millions	Dec. 31, 2018	Mar. 31, 2018	[1]
Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset	$ 2.3	$ 0.3
Accounts Payable and Accrued Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability	0.9	0.6
Other Non-Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability	35.1
Forward exchange contracts | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset	2.3	0.3
Forward exchange contracts | Accounts Payable and Accrued Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability	0.9	$ 0.6
Forward exchange contracts | Other Non-Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability	0.0
Interest rate swap agreements | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset	0.0
Interest rate swap agreements | Accounts Payable and Accrued Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability	0.0
Interest rate swap agreements | Other Non-Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability	$ 35.1

[1] Includes an immaterial amount of forward foreign exchange contracts not designated as hedging instruments as of March 31, 2018.