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Share-Based Compensation Plans - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended 1 Months Ended 3 Months Ended
Jun. 30, 2013
CompensationPlan
Apr. 17, 2013
2012 Long Term Incentive Plan
Jun. 30, 2013
2012 Long Term Incentive Plan
Jun. 30, 2013
Directors Plan
Mar. 31, 2013
Performance Restricted Stock Units
Mar. 31, 2012
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Additional shares authorized   2,000,000        
Number of remaining shares that may be issued     5,462,265 39,843    
Number of employee stock purchase programs 2          
Awards requisite service period         3 years  
Fair value assumptions, risk-free interest rate         0.42% 0.41%
Fair value assumptions, dividend yield         0.81% 0.85%
Fair value assumptions, expected life in years         2 years 10 months 17 days 2 years 9 months 29 days
Unrecognized compensation expenses related to share-based payment arrangements $ 85.0          
Weighted-average period of recognizing unrecognized compensation expenses related to share-based compensation, in years 2 years