Quarterly report pursuant to Section 13 or 15(d)

Net Income Per Share (Details)

v3.10.0.1
Net Income Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Earnings Per Share, Basic, Two Class Method [Abstract]        
Net income and comprehensive income $ 24,298 $ 19,666 $ 42,038 $ 34,246
Income allocated to participating securities (209) (160) (359) (281)
Numerator for basic and diluted income per share - net income $ 24,089 $ 19,506 $ 41,679 $ 33,965
Denominator for basic income per share - weighted-average shares 29,169 30,026 29,288 30,029
Denominator for diluted income per share - adjusted weighted-average shares 29,272 30,114 29,391 30,127
Basic income per share (dollars per share) $ 0.83 $ 0.65 $ 1.42 $ 1.13
Diluted income per share (dollars per share) $ 0.82 $ 0.65 $ 1.42 $ 1.13
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     102 303
Equity Option [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 74 61 71 68
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     82 284
Key Employee Performance Share Based Plan [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 29 27 32 30
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     15 19
Nonvested Shares and Deferred Stock Units [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     5 0