Quarterly report pursuant to Section 13 or 15(d)

Net Income Per Share (Details)

v3.8.0.1
Net Income Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Earnings Per Share, Basic, Two Class Method [Abstract]        
Net income and comprehensive income $ 18,155 $ 11,931 $ 51,948 $ 14,964
Income allocated to participating securities (145) (93) (419) (114)
Numerator for basic and diluted income per share - net income $ 18,010 $ 11,838 $ 51,529 $ 14,850
Denominator for basic income per share - weighted-average shares 29,855 30,191 29,977 30,316
Denominator for diluted income per share - adjusted weighted-average shares 29,940 30,338 30,069 30,496
Basic income per share (dollars per share) $ 0.60 $ 0.39 $ 1.72 $ 0.49
Diluted income per share (dollars per share) $ 0.60 $ 0.39 $ 1.71 $ 0.49
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     172 309
Equity Option [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 52 117 62 151
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     172 309
Key Employee Performance Share Based Plan [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 33 30 30 29
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     0 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     0 0