Computation of Net Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Sep. 30, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Computation of net earnings per share | |||||
| Net earnings | $ 2,753 | $ 11,097 | $ 15,737 | $ 21,476 | $ 40,384 |
| Average basic shares outstanding (shares) | 11,018 | 11,321 | 11,022 | 11,385 | |
| Basic net earnings per share (usd per share) | $ 0.25 | $ 1.39 | $ 1.95 | $ 3.55 | |
| Average diluted shares outstanding (shares) | 11,084 | 11,383 | 11,105 | 11,474 | |
| Diluted net earnings per share (usd per share) | $ 0.25 | $ 1.38 | $ 1.93 | $ 3.52 | |
| Restricted stock not vested | |||||
| Computation of net earnings per share | |||||
| Dilutive shares (shares) | 27 | 18 | 24 | 16 | |
| Dilutive effect of Performance Share Plan | |||||
| Computation of net earnings per share | |||||
| Dilutive shares (shares) | 39 | 45 | 59 | 73 | |