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Earnings per Share - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Earnings Per Share [Line Items]    
Dividends paid on common stock $ 14,504 $ 12,715
First Quarter Dividend [Member]    
Earnings Per Share [Line Items]    
Dividend record date Mar. 01, 2018 Mar. 01, 2017
Dividend paid date Mar. 15, 2018 Mar. 15, 2017
Quarterly cash dividend paid $ 0.07 $ 0.0625
Stock Options [Member]    
Earnings Per Share [Line Items]    
Options to purchase shares outstanding 182,333 14,455,614