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Restricted Stock, Stock Options and Other Stock Plans - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 14, 2004
Dec. 31, 2018
Dec. 31, 2017
Nov. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Weighted-average remaining contractual term of unexercised stock options   7 years 8 months 12 days 8 years 6 months  
Class A [Member] | November 2014 New Share Repurchase Program [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Remaining common stock available for repurchase under share repurchase program   404,000 404,000  
2004 Long-Term Compensation Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized compensation cost related to stock issuances   $ 0.3 $ 0.6  
2004 Long-Term Compensation Plan [Member] | Class A [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Authorized increase in number of shares   1,000,000    
Description of additional shares authorized for issuance under long-term compensation plan   The Plan authorized 1.0 million shares of our Class A Common Stock with an automatic annual increase on January 1 of each successive year of the lesser of (i) 3% of the Class A common stock outstanding or (ii) 107 shares.    
Percentage of additional shares authorized issuable under long-term compensation plan   3.00%    
Shares issued   107    
Shares available for issuance under long-term compensation plan   60,000 400,000  
Stock Options [Member] | 2004 Long-Term Compensation Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Long-term compensation plan stock option expiration period 10 years      
Weighted-average remaining contractual term of unexercised stock options   7 years 8 months 1 day 8 years 6 months  
Minimum [Member] | 2004 Long-Term Compensation Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Long-term compensation plan vesting period 1 year      
Maximum [Member] | Class A [Member] | November 2014 New Share Repurchase Program [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
New share repurchase program, shares authorized to repurchase       429,000
Maximum [Member] | 2004 Long-Term Compensation Plan [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Long-term compensation plan vesting period 5 years