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 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Earnings Per Share, Basic, Two Class Method [Abstract]        
Net income and comprehensive income $ 22,329 $ 18,328 $ 64,366 $ 52,575
Income allocated to participating securities (239) (146) (596) (424)
Numerator for basic and diluted income per share - net income $ 22,090 $ 18,182 $ 63,770 $ 52,151
Denominator for basic income per share - weighted-average shares 28,964 29,855 29,189 29,977
Denominator for diluted income per share - adjusted weighted-average shares 29,095 29,940 29,303 30,069
Basic income per share (dollars per share) $ 0.76 $ 0.61 $ 2.18 $ 1.74
Diluted income per share (dollars per share) $ 0.76 $ 0.61 $ 2.18 $ 1.73
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     118 172
Equity Option [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 95 52 81 62
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     100 172
Key Employee Performance Share Based Plan [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 36 33 33 30
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     15 0
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     3 0