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

Property, Plant and Equipment - Components of Property, Plant and Equipment 2 (Detail)

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Property, Plant and Equipment - Components of Property, Plant and Equipment 2 (Detail) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Property, Plant and Equipment [Line Items]      
Capitalized interest $ 4.8 $ 2.0 $ 3.2
Net book value of disposals 16.4    
Net book value of disposals, usage of replacement parts 13.9    
Net book value of disposals, disposal of assets no longer in use 1.8    
Fontana Building [Member] | Held-for-sale [Member] | Buildings [Member]      
Property, Plant and Equipment [Line Items]      
Buildings held for sale   $ 4.5  
Fontana Building [Member] | Disposed of by Sale [Member] | Buildings [Member]      
Property, Plant and Equipment [Line Items]      
Sale price of disposal 7.9    
Gain from disposition $ 3.4