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Stock-Based Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
6 Months Ended 1 Months Ended 3 Months Ended
Jun. 30, 2013
Jun. 30, 2013
Stock options
Minimum
Jun. 30, 2013
Stock options
Maximum
Apr. 30, 2011
Performance share units
Jun. 30, 2013
Performance share units
Dec. 31, 2012
Performance share units
Jun. 30, 2013
Performance Shares 2012 Awards
Jun. 30, 2013
Performance Shares 2013 Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Stock options vesting period   3 years 4 years 1 year        
Stock options remaining contractual term 10 years              
Number of performance share units       190,250 373,000 343,000 206,000  
Vesting date       2013-12        
Compensation expense             $ 5.9 $ 1.0
Unrecognized compensation expense             $ 2.3 $ 6.8
Percentage of Compensation Expense               60.00%