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Share-Based Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Mar. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based compensation $ 3.8 $ 4.0  
Stock Options
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based compensation 0.3 0.4  
Intrinsic value of options exercised 1.0    
Unrecognized share-based compensation cost 1.4    
Unrecognized compensation expense, weighted-average period of recognition 1 year 9 months 18 days    
Excess tax benefits shown as financing cash inflows 0.3    
Restricted stock units
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based compensation 2.9 3.2  
Unrecognized share-based compensation cost 21.1    
Unrecognized compensation expense, weighted-average period of recognition 2 years 7 months 6 days    
Excess tax benefits shown as financing cash inflows 2.2 1.3  
Equity instruments other than options expected to vest, Shares 1,900,000    
Equity instruments other than options expected to vest, weighted-average grant date fair value $ 12.54    
Performance Shares
     
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based compensation 0.6 0.4  
Unrecognized share-based compensation cost $ 8.2    
Unrecognized compensation expense, weighted-average period of recognition 2 years 4 months 24 days    
Performance share unit awards granted to certain executive officers 319,000    
Equity instruments other than options, payout range, minimum 154,500    
Equity instruments other than options, payout range, maximum 319,000 485,000 233,000
Compensation expense achieved target, shares 121,431    
Compensation expense achieved target, percentage 52.00%