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

Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail)

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Cash and Cash Equivalents - Summary of Cash and Cash Equivalents (Detail) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
Mar. 31, 2012
Mar. 31, 2011
Mar. 31, 2010
Cash and Cash Equivalents [Line Items]        
Cash at bank and on hand $ 55.5 $ 256.1 $ 9.5  
Short-term deposits 98.2 9.3 9.1  
Cash and cash equivalents at end of period $ 153.7 $ 265.4 $ 18.6 $ 19.2