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Stock-Based Compensation and Stock Awards - Stock Options - Additional Information (Detail)
12 Months Ended
May 13, 2004
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
shares
Dec. 31, 2015
USD ($)
shares
May 12, 2017
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Common stock reserved (up to) (in shares) | shares   280,212 351,959   1,500,000
Intrinsic value of stock options exercised   $ 400,000 $ 1,000,000 $ 800,000  
Anti-dilutive awards (in shares) | shares   21,483 186,112    
Stock-based compensation expense for stock option exercises     $ 0 1,100,000  
Capitalized expense   $ 0 0 0  
Stock Options          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Income tax benefit realized from stock options exercised   $ 153,759 $ 357,000,000 $ 263,000,000  
Anti-dilutive awards (in shares) | shares   21,000 0 0  
Unrecognized compensation expense related to share based compensation   $ 0      
2004 Plan          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Options granted period 10 years        
Cumulative annual increments of the total number of shares 0.25        
2004 Plan | Stock Options          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Vesting period (in years) 4 years