Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Immaterial Change in Statement of Cash Flows Line Items (Details)

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Summary of Significant Accounting Policies - Immaterial Change in Statement of Cash Flows Line Items (Details) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Net cash provided by operating activities $ 451.2 $ 304.0 $ 308.5
Purchases of property, plant and equipment (193.8) (317.5) (210.2)
Net cash used in investing activities $ (203.8) (864.4) (245.5)
As reported      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Accounts payable and accrued liabilities   (12.9) 14.2
Net cash provided by operating activities   287.6 302.0
Purchases of property, plant and equipment   (301.1) (203.7)
Net cash used in investing activities   (848.0) (239.0)
As adjusted      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]      
Accounts payable and accrued liabilities   3.5 20.7
Net cash provided by operating activities   304.0 308.5
Purchases of property, plant and equipment   (317.5) (210.2)
Net cash used in investing activities   $ (864.4) $ (245.5)