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

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) - Component of Accumulated Other Comprehensive Income (Detail)

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Reclassifications Out of Accumulated Other Comprehensive Income (Loss) - Component of Accumulated Other Comprehensive Income (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Mar. 31, 2011
Reclassifications Out Of Accumulated Other Comprehensive Income [Line Items]      
Beginning balance, Pension and Post-Retirement Benefit Adjustment $ (0.3)    
Other comprehensive income before reclassifications, Pension and Post-Retirement Benefit Adjustment       
Amounts reclassified from accumulated other comprehensive income to interest income, Pension and Post-Retirement Benefit Adjustment       
Net current-period other comprehensive income, Pension and Post-Retirement Benefit Adjustment      (1.3)
Ending balance, Pension and Post-Retirement Benefit Adjustment (0.3) (0.3)  
Beginning balance, Unrealised Gain on Investments 2.6    
Other comprehensive income before reclassifications, Unrealised Gain on Investments 3.6    
Amounts reclassified from accumulated other comprehensive income to interest income, Unrealised Gain on Investments (2.7)    
Net current-period other comprehensive income, Unrealised Gain on Investments 0.9    
Ending balance, Unrealised Gain on Investments 3.5 2.6  
Beginning balance, Foreign Currency Translation Adjustments 47.1    
Other comprehensive income before reclassifications, Foreign Currency Translation Adjustments (2.9) (5.9) (6.6)
Amounts reclassified from accumulated other comprehensive income to interest income, Foreign Currency Translation Adjustments       
Net current-period other comprehensive income, Foreign Currency Translation Adjustments (2.9)    
Ending balance, Foreign Currency Translation Adjustments 44.2 47.1  
Beginning balance 49.4    
Other comprehensive income before reclassifications 0.7    
Amounts reclassified from accumulated other comprehensive income to interest income (2.7)    
Net current-period other comprehensive income (2.0) (5.8) (4.0)
Ending balance $ 47.4 $ 49.4