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Shareholders' Equity Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
Mar. 31, 2019
Jun. 30, 2018
Mar. 31, 2018
Jun. 30, 2019
Jun. 30, 2018
Equity [Abstract]            
Repurchase and retirement of common stock $ 427 $ 6,110 $ 177,380 $ 14,987 $ 6,537  
Repurchase and retirement of common stock (shares)         76,000  
Stock Repurchase Program, Number of Shares Authorized to be Repurchased 3,175,000       3,175,000  
Cash dividend paid during period, per share (in dollars per share) $ 0.61   $ 0.60   $ 1.22 $ 1.20
Common stock excluded from calculation of diluted earnings per share (shares) 4,045,000   1,812,000   4,069,000 1,677,000