Quarterly report pursuant to Section 13 or 15(d)

Net Income Per Share (Details)

v3.7.0.1
Net Income Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Earnings Per Share, Basic, Two Class Method [Abstract]        
Net income and comprehensive income $ 19,550 $ (10,066) $ 33,793 $ 3,033
Income allocated to participating securities (159) (28) (278) (55)
Numerator for basic and diluted income per share - net income $ 19,391 $ (10,094) $ 33,515 $ 2,978
Denominator for basic income per share - weighted-average shares 30,026 30,252 30,029 30,356
Denominator for diluted income per share - adjusted weighted-average shares 30,114 30,252 30,127 30,557
Basic income per share (dollars per share) $ 0.65 $ (0.33) $ 1.12 $ 0.10
Diluted income per share (dollars per share) $ 0.64 $ (0.33) $ 1.11 $ 0.10
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     303 324
Equity Option [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 61 0 68 169
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     284 301
Key Employee Performance Share Based Plan [Member]        
Earnings Per Share, Basic, Two Class Method [Abstract]        
Effect of dilutive stock options and non-vested shares 27 0 30 32
Total number anti-dilutive options, non-vested shares, and performance shares excluded from income per diluted share computation     19 23
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