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Stock-Based Compensation - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 9 Months Ended 3 Months Ended 9 Months Ended 3 Months Ended 9 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Restricted Stock [Member]
Sep. 30, 2012
Restricted Stock [Member]
Sep. 30, 2013
Restricted Stock [Member]
Sep. 30, 2012
Restricted Stock [Member]
Sep. 30, 2013
Restricted Stock [Member]
Minimum [Member]
Sep. 30, 2013
Restricted Stock [Member]
Maximum [Member]
Sep. 30, 2013
Performance Share Units [Member]
Sep. 30, 2012
Performance Share Units [Member]
Sep. 30, 2013
Performance Share Units [Member]
Sep. 30, 2012
Performance Share Units [Member]
Sep. 30, 2013
Performance Share Units [Member]
Minimum [Member]
Sep. 30, 2013
Performance Share Units [Member]
Maximum [Member]
Sep. 30, 2013
PSU 2013 Grants [Member]
Feb. 15, 2013
PSU 2013 Grants [Member]
Sep. 30, 2013
PSU 2012 Grants [Member]
Jul. 30, 2012
PSU 2012 Grants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                    
Award vesting period         3 years                          
Annual forfeiture rate             0.00% 11.00%     2.70%              
Stock-based compensation expense $ 8,411 $ 6,627 $ 2,600 $ 2,600 $ 7,100 $ 6,500     $ 500 $ 200 $ 1,300 $ 200            
Right to received shares of common stock                 1   1              
Performance share units initial performance period, years                     3 years              
PSU granted percentage of earnings                         0.00% 200.00%        
Amortized performance period                     4 years       4 years   4 years 2 days  
Number of trading days                     30 days              
Valuation model standard deviation term                     2 years              
Expected percentage earned                               112.00%   98.00%