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Earnings Per Share - Additional Information (Detail) - shares
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Options excluded from the computation of diluted earnings 0 0 0 0
Class A Common Stock [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Common stock, voting rights     One vote per share  
Class B Common Stock [Member]        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Common stock, voting rights     Ten votes per share