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 (Detail)

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Property, Plant and Equipment - Components of Property, Plant and Equipment (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Property, Plant and Equipment [Line Items]    
Cost, Beginning balance $ 1,264.6 $ 1,253.1
Additions 61.1 35.8
Disposals (7.3) (2.9)
Impairment (37.1) (26.0)
Exchange differences 3.2 4.1
Other   0.5
Cost, Ending balance 1,284.5 1,264.6
Accumulated depreciation, Beginning balance (589.9) (536.7)
Charge for the year (60.0) (65.2)
Disposals 6.5 2.6
Impairment 20.2 11.7
Exchange differences (1.8) (2.3)
Other (0.6)  
Accumulated depreciation, Ending balance (625.6) (589.9)
Net book amount 658.9 674.7
Land [Member]
    
Property, Plant and Equipment [Line Items]    
Cost, Beginning balance 18.3 18.3
Additions 0.2   
Disposals     
Impairment     
Exchange differences     
Other     
Cost, Ending balance 18.5 18.3
Net book amount 18.5 18.3
Buildings [Member]
    
Property, Plant and Equipment [Line Items]    
Cost, Beginning balance 210.5 210.4
Additions 3.0  
Impairment (3.5)  
Exchange differences 0.2 0.1
Cost, Ending balance 210.2 210.5
Accumulated depreciation, Beginning balance (76.2) (67.3)
Charge for the year (8.8) (8.8)
Exchange differences (0.2) (0.1)
Accumulated depreciation, Ending balance (85.2) (76.2)
Net book amount 125.0 134.3
Machinery and Equipment [Member]
    
Property, Plant and Equipment [Line Items]    
Cost, Beginning balance 984.9 981.2
Additions 47.7 28.6
Disposals (7.3) (2.9)
Impairment (33.6) (26.0)
Exchange differences 3.0 4.0
Cost, Ending balance 994.7 984.9
Accumulated depreciation, Beginning balance (513.7) (469.4)
Charge for the year (51.2) (56.4)
Disposals 6.5 2.6
Impairment 20.2 11.7
Exchange differences (1.6) (2.2)
Other (0.6)  
Accumulated depreciation, Ending balance (540.4) (513.7)
Net book amount 454.3 471.2
Construction in Progress [Member]
    
Property, Plant and Equipment [Line Items]    
Cost, Beginning balance 50.9 43.2
Additions 10.2 7.2
Other   0.5
Cost, Ending balance 61.1 50.9
Net book amount $ 61.1 $ 50.9