| Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Earnings per share – basic: | | | | | | | | | | | | | | | | | | Net income | | $ | 19,738 | | | $ | 22,167 | | | $ | 84,449 | | | $ | 48,476 | | | Income allocated to participating securities | | | (18 | ) | | | (20 | ) | | | (70 | ) | | | (42 | ) | | Income available to common shareholders | | $ | 19,720 | | | $ | 22,147 | | | $ | 84,379 | | | $ | 48,434 | | | Weighted-average shares outstanding – basic | | | 37,503 | | | | 37,320 | | | | 37,450 | | | | 37,303 | | | Earnings per share – basic | | $ | 0.53 | | | $ | 0.59 | | | $ | 2.25 | | | $ | 1.30 | | | | | | | | | | | | | | | | | | | | | Earnings per share – diluted: | | | | | | | | | | | | | | | | | | Net income | | $ | 19,738 | | | $ | 22,167 | | | $ | 84,449 | | | $ | 48,476 | | | Income allocated to participating securities | | | (18 | ) | | | (20 | ) | | | (70 | ) | | | (42 | ) | | Income available to common shareholders | | $ | 19,720 | | | $ | 22,147 | | | $ | 84,379 | | | $ | 48,434 | | | Weighted-average shares outstanding – basic | | | 37,503 | | | | 37,320 | | | | 37,450 | | | | 37,303 | | | Dilutive effect of stock options and restricted stock units | | | 639 | | | | 174 | | | | 483 | | | | 183 | | | Weighted-average common shares outstanding – diluted | | | 38,142 | | | | 37,494 | | | | 37,933 | | | | 37,486 | | | Earnings per share – diluted | | $ | 0.52 | | | $ | 0.59 | | | $ | 2.22 | | | $ | 1.29 | | |