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Earnings per Share - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Mar. 30, 2016
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Earnings Per Share [Line Items]          
Dividends paid on common stock       $ 24,790 $ 21,101
First Quarter Dividend [Member]          
Earnings Per Share [Line Items]          
Quarterly cash dividend paid       $ 0.0625  
Dividend record date       Mar. 07, 2016  
Dividend paid date       Mar. 15, 2016  
Second Quarter Dividend [Member]          
Earnings Per Share [Line Items]          
Quarterly cash dividend paid       $ 0.0625  
Dividend record date       Jun. 01, 2016  
Dividend paid date       Jun. 15, 2016  
Class A Non-Voting Common Stock [Member]          
Earnings Per Share [Line Items]          
Conversion of common stock number of shares converted 2,703,846        
Conversion of common stock number of shares issued 2,703,846        
Common stock convertible conversion ratio       100.00%  
Stock Options [Member]          
Earnings Per Share [Line Items]          
Options to purchase shares outstanding   7,304,581 4,122,738 7,075,350 4,119,018