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Stock-Based Compensation - Additional Information (Detail) (USD $)
In Millions, except Per Share data, unless otherwise specified
6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Recognized stock-based compensation expense $ 2.6 $ 3.8
Unearned compensation cost related to the unvested portion of all stock-based awards $ 8.9  
Stock Options [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of share based compensation units granted 0.6  
Performance Share Units [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of share based compensation units granted 0.5  
Weighted average grant date fair value $ 5.70  
Deferred Stock Units [Member]
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Number of share based compensation units granted 0.3  
Weighted-average fair value per unit $ 5.52