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Stock-Based Compensation - Additional Information (Detail) (USD $)
3 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Aggregate intrinsic value of options exercised in period $ 2,500,000    
Fair value of options vested in period 2,000,000    
Expected dividend yield 0.00%    
Stock-based compensation 2,679,000 2,332,000  
Stock Options
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized stock-based compensation expense 5,000,000    
Unrecognized stock-based compensation expense, weighted-average recognition period 2 years 10 months 24 days    
Performance Based Restricted Stock and Restricted Stock Units
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized stock-based compensation expense 6,800,000    
Unrecognized stock-based compensation expense, weighted-average recognition period 2 years 4 months 24 days    
Shares of award granted 195,188 284,000 311,000
Shares of award granted, performance target met 184,000    
Shares of award granted, it is probable that the prescribed performance targets will be met 100,000    
Stock-based compensation 900,000    
Restricted Stock and Restricted Stock Units
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized stock-based compensation expense 12,600,000    
Unrecognized stock-based compensation expense, weighted-average recognition period 2 years 4 months 24 days    
Weighted average grant-date fair value for restricted stock and restricted stock units granted $ 22.40 18.49  
Fair value of restricted stock and restricted stock units vested in period $ 2,900,000 1,500,000  
Shares of award granted 361,000    
Performance Shares
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares of award granted     45,000