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, 2015
Mar. 31, 2014
Mar. 31, 2013
Mar. 31, 2012
Cash and Cash Equivalents [Abstract]        
Cash at bank and on hand $ 60.0us-gaap_Cash $ 70.9us-gaap_Cash $ 55.5us-gaap_Cash  
Short-term deposits 7.0us-gaap_CashEquivalentsAtCarryingValue 96.6us-gaap_CashEquivalentsAtCarryingValue 98.2us-gaap_CashEquivalentsAtCarryingValue  
Total cash and cash equivalents $ 67.0us-gaap_CashAndCashEquivalentsAtCarryingValue $ 167.5us-gaap_CashAndCashEquivalentsAtCarryingValue $ 153.7us-gaap_CashAndCashEquivalentsAtCarryingValue $ 265.4us-gaap_CashAndCashEquivalentsAtCarryingValue