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Stock-Based Compensation - Additional Information (Detail) (USD $)
 6 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Restricted Stock [Member]
Jun. 30, 2012
Restricted Stock [Member]
Jun. 30, 2013
Restricted Stock [Member]
Jun. 30, 2012
Restricted Stock [Member]
Jun. 30, 2013
Restricted Stock [Member]
Minimum [Member]
Jun. 30, 2013
Restricted Stock [Member]
Maximum [Member]
Jun. 30, 2013
Performance Share Units [Member]
Jun. 30, 2012
Performance Share Units [Member]
Jun. 30, 2013
Performance Share Units [Member]
Jun. 30, 2012
Performance Share Units [Member]
Jun. 30, 2013
Performance Share Units [Member]
Minimum [Member]
Jun. 30, 2013
Performance Share Units [Member]
Maximum [Member]
Jun. 30, 2013
PSU 2013 Grants [Member]
Feb. 15, 2013
PSU 2013 Grants [Member]
Jun. 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 $ 5,371,000 $ 3,898,000 $ 2,600,000 $ 2,300,000 $ 4,600,000 $ 3,900,000     $ 500,000 $ 0 $ 800,000 $ 0            
Right to received shares of common stock                 1   1              
Performance share units initial performance period, years                     3 years              
Amortized performance period                     4 years       4 years   4 years 2 days  
PSU granted percentage of earnings                         0.00% 200.00%        
Number of trading days                     30 days              
Expected percentage earned                               112.00%   98.00%